From acaa35ae580362599b0ff4e1b3811edd2159a78e Mon Sep 17 00:00:00 2001
From: Ivan Enderlin <ivan.enderlin@hoa-project.net>
Date: Wed, 20 Feb 2019 15:42:57 +0100
Subject: [PATCH] chore(php) Move to PHP 7.1.

---
 Dal.php => Source/Dal.php                     | 147 ++++--------------
 DalStatement.php => Source/DalStatement.php   | 106 +++----------
 Exception.php => Source/Exception.php         |   5 +-
 {IDal => Source/IDal}/Wrapper.php             |  99 +++---------
 {IDal => Source/IDal}/WrapperIterator.php     |  10 +-
 {IDal => Source/IDal}/WrapperStatement.php    |  85 +++-------
 {Layer => Source/Layer}/Dba/Dba.php           |   0
 {Layer => Source/Layer}/Dba/DbaStatement.php  |   0
 {Layer => Source/Layer}/Dbx/Dbx.php           |   0
 {Layer => Source/Layer}/Dbx/DbxStatement.php  |   0
 {Layer => Source/Layer}/Odbc/Odbc.php         |   0
 .../Layer}/Odbc/OdbcStatement.php             |   0
 {Layer => Source/Layer}/Pdo/Iterator.php      |  28 +---
 {Layer => Source/Layer}/Pdo/Pdo.php           | 111 +++----------
 {Layer => Source/Layer}/Pdo/Statement.php     | 108 +++----------
 {Query => Source/Query}/Delete.php            |  16 +-
 {Query => Source/Query}/Dml.php               |  20 +--
 {Query => Source/Query}/EncloseIdentifier.php |  24 +--
 {Query => Source/Query}/Insert.php            |  80 +++-------
 {Query => Source/Query}/Join.php              |  27 +---
 {Query => Source/Query}/Query.php             |  56 ++-----
 {Query => Source/Query}/Select.php            |  55 ++-----
 {Query => Source/Query}/SelectCore.php        | 123 ++++-----------
 {Query => Source/Query}/Update.php            |  49 ++----
 {Query => Source/Query}/Where.php             |  35 ++---
 Test/Unit/Query/EncloseIdentifier.php         |  11 +-
 Test/Unit/Query/Example.php                   |   7 +-
 composer.json                                 |  19 +--
 28 files changed, 293 insertions(+), 928 deletions(-)
 rename Dal.php => Source/Dal.php (72%)
 rename DalStatement.php => Source/DalStatement.php (71%)
 rename Exception.php => Source/Exception.php (95%)
 rename {IDal => Source/IDal}/Wrapper.php (50%)
 rename {IDal => Source/IDal}/WrapperIterator.php (86%)
 rename {IDal => Source/IDal}/WrapperStatement.php (52%)
 rename {Layer => Source/Layer}/Dba/Dba.php (100%)
 rename {Layer => Source/Layer}/Dba/DbaStatement.php (100%)
 rename {Layer => Source/Layer}/Dbx/Dbx.php (100%)
 rename {Layer => Source/Layer}/Dbx/DbxStatement.php (100%)
 rename {Layer => Source/Layer}/Odbc/Odbc.php (100%)
 rename {Layer => Source/Layer}/Odbc/OdbcStatement.php (100%)
 rename {Layer => Source/Layer}/Pdo/Iterator.php (88%)
 rename {Layer => Source/Layer}/Pdo/Pdo.php (68%)
 rename {Layer => Source/Layer}/Pdo/Statement.php (63%)
 rename {Query => Source/Query}/Delete.php (87%)
 rename {Query => Source/Query}/Dml.php (78%)
 rename {Query => Source/Query}/EncloseIdentifier.php (82%)
 rename {Query => Source/Query}/Insert.php (73%)
 rename {Query => Source/Query}/Join.php (77%)
 rename {Query => Source/Query}/Query.php (72%)
 rename {Query => Source/Query}/Select.php (77%)
 rename {Query => Source/Query}/SelectCore.php (70%)
 rename {Query => Source/Query}/Update.php (76%)
 rename {Query => Source/Query}/Where.php (79%)

diff --git a/Dal.php b/Source/Dal.php
similarity index 72%
rename from Dal.php
rename to Source/Dal.php
index 4cc3e08..8a7eca7 100644
--- a/Dal.php
+++ b/Source/Dal.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * Hoa
  *
@@ -44,9 +46,6 @@
  * Class \Hoa\Database\Dal.
  *
  * The higher class of the Database Abstract Layer. It wrappes all DAL.
- *
- * @copyright  Copyright © 2007-2017 Hoa community
- * @license    New BSD License
  */
 class Dal implements Zformat\Parameterizable, Event\Source
 {
@@ -102,14 +101,14 @@ class Dal implements Zformat\Parameterizable, Event\Source
     /**
      * The layer instance.
      *
-     * @var \Hoa\Database\IDal\Wrapper
+     * @var ?IDal\Wrapper
      */
     protected $_layer                = null;
 
     /**
      * Parameter of \Hoa\Database\Dal.
      *
-     * @var \Hoa\Zformat\Parameter
+     * @var ?Zformat\Parameter
      */
     protected static $_parameters    = null;
 
@@ -125,8 +124,6 @@ class Dal implements Zformat\Parameterizable, Event\Source
     /**
      * Create a DAL instance, representing a connection to a database.
      * The constructor is private to make a multiton.
-     *
-     * @param   array   $connectionParameters    The layer connection parameter.
      */
     private function __construct(array $connectionParameters)
     {
@@ -143,9 +140,6 @@ private function __construct(array $connectionParameters)
 
     /**
      * Initialize parameters.
-     *
-     * @param   array  $parameters    Parameters.
-     * @return  void
      */
     public static function initializeParameters(array $parameters = [])
     {
@@ -172,24 +166,15 @@ public static function initializeParameters(array $parameters = [])
 
     /**
      * Make a multiton on the $id.
-     *
-     * @param   string  $id               The instance ID.
-     * @param   string  $dalName          The database abstract layer name.
-     * @param   string  $dsn              The DSN of database.
-     * @param   string  $username         The username to connect to database.
-     * @param   string  $password         The password to connect to database.
-     * @param   array   $driverOptions    The driver options.
-     * @return  \Hoa\Database\Dal
-     * @throws  \Hoa\Database\Exception
      */
     public static function getInstance(
-        $id,
-        $dalName             = null,
-        $dsn                 = null,
-        $username            = null,
-        $password            = null,
+        string $id,
+        string $dalName             = null,
+        string $dsn                 = null,
+        string $username            = null,
+        string $password            = null,
         array $driverOptions = []
-    ) {
+    ): self {
         if (null === self::$_parameters) {
             self::initializeParameters();
         }
@@ -236,11 +221,8 @@ public static function getInstance(
      * Get the last instance of a DAL, i.e. the last used singleton.
      * If no instance was set but if the connection.autoload parameter is set,
      * then we auto-connect (autoload) a connection.
-     *
-     * @return  \Hoa\Database\IDal\Wrapper
-     * @throws  \Hoa\Database\Exception
      */
-    public static function getLastInstance()
+    public static function getLastInstance(): IDal\Wrapper
     {
         if (null === self::$_parameters) {
             self::initializeParameters();
@@ -268,18 +250,14 @@ public static function getLastInstance()
 
     /**
      * Get parameters.
-     *
-     * @return  \Hoa\Zformat\Parameter
      */
-    public function getParameters()
+    public function getParameters(): ?Zformat\Parameter
     {
         return self::$_parameters;
     }
 
     /**
      * Open a connection to the database.
-     *
-     * @return  void
      */
     private function open()
     {
@@ -320,10 +298,8 @@ private function open()
 
     /**
      * Close connection to the database.
-     *
-     * @return  bool
      */
-    public function close()
+    public function close(): bool
     {
         $id    = $this->getId();
         $event = 'hoa://Event/Database/' . $id;
@@ -346,11 +322,8 @@ public function close()
 
     /**
      * Set database abstract layer instance.
-     *
-     * @param   \Hoa\Database\IDal\Wrapper  $dal    The DAL instance.
-     * @return  \Hoa\Database\IDal\Wrapper
      */
-    protected function setDal(IDal\Wrapper $dal)
+    protected function setDal(IDal\Wrapper $dal): ?IDal\Wrapper
     {
         $old          = $this->_layer;
         $this->_layer = $dal;
@@ -360,10 +333,8 @@ protected function setDal(IDal\Wrapper $dal)
 
     /**
      * Get the database abstract layer instance.
-     *
-     * @return  \Hoa\Database\IDal\Wrapper
      */
-    protected function getDal()
+    protected function getDal(): ?IDal\Wrapper
     {
         if (null === $this->_layer) {
             $this->open();
@@ -374,46 +345,32 @@ protected function getDal()
 
     /**
      * Initiate a transaction.
-     *
-     * @return  bool
-     * @throws  \Hoa\Database\Exception
      */
-    public function beginTransaction()
+    public function beginTransaction(): bool
     {
         return $this->getDal()->beginTransaction();
     }
 
     /**
      * Commit a transaction.
-     *
-     * @return  bool
-     * @throws  \Hoa\Database\Exception
      */
-    public function commit()
+    public function commit(): bool
     {
         return $this->getDal()->commit();
     }
 
     /**
      * Roll back a transaction.
-     *
-     * @return  bool
-     * @throws  \Hoa\Database\Exception
      */
-    public function rollBack()
+    public function rollBack(): bool
     {
         return $this->getDal()->rollBack();
     }
 
     /**
      * Return the ID of the last inserted row or sequence value.
-     *
-     * @param   string  $name    Name of sequence object (needed for some
-     *                           driver).
-     * @return  string
-     * @throws  \Hoa\Database\Exception
      */
-    public function lastInsertId($name = null)
+    public function lastInsertId(string $name = null): string
     {
         if (null === $name) {
             return $this->getDal()->lastInsertId();
@@ -424,15 +381,8 @@ public function lastInsertId($name = null)
 
     /**
      * Prepare a statement for execution and returns a statement object.
-     *
-     * @param   string  $statement    This must be a valid SQL statement for the
-     *                                target database server.
-     * @param   array   $options      Options to set attributes values for the
-     *                                layer statement.
-     * @return  \Hoa\Database\DalStatement
-     * @throws  \Hoa\Database\Exception
-     */
-    public function prepare($statement, array $options = [])
+     */
+    public function prepare(string $statement, array $options = []): DalStatement
     {
         return new DalStatement(
             $this->getDal()->prepare(
@@ -443,14 +393,8 @@ public function prepare($statement, array $options = [])
 
     /**
      * Quote a string for use in a query.
-     *
-     * @param   string  $string    The string to be quoted.
-     * @param   int     $type      Provide a data type hint for drivers that
-     *                             have alternate quoting styles.
-     * @return  string
-     * @throws  \Hoa\Database\Exception
      */
-    public function quote($string = null, $type = -1)
+    public function quote(?string $string, int $type = -1): string
     {
         if ($type < 0) {
             return $this->getDal()->quote($string);
@@ -462,12 +406,8 @@ public function quote($string = null, $type = -1)
     /**
      * Execute an SQL statement, returning a result set as a
      * \Hoa\Database\DalStatement object.
-     *
-     * @param   string  $statement    The SQL statement to prepare and execute.
-     * @return  \Hoa\Database\DalStatement
-     * @throws  \Hoa\Database\Exception
      */
-    public function query($statement)
+    public function query(string $statement): DalStatement
     {
         return new DalStatement(
             $this->getDal()->query($statement)
@@ -477,11 +417,8 @@ public function query($statement)
     /**
      * Fetch the SQLSTATE associated with the last operation on the database
      * handle.
-     *
-     * @return  string
-     * @throws  \Hoa\Database\Exception
      */
-    public function errorCode()
+    public function errorCode(): string
     {
         return $this->getDal()->errorCode();
     }
@@ -489,45 +426,30 @@ public function errorCode()
     /**
      * Fetch extends error information associated with the last operation on the
      * database handle.
-     *
-     * @return  array
-     * @throws  \Hoa\Database\Exception
      */
-    public function errorInfo()
+    public function errorInfo(): array
     {
         return $this->getDal()->errorInfo();
     }
 
     /**
      * Return an array of available drivers.
-     *
-     * @return  array
-     * @throws  \Hoa\Database\Exception
      */
-    public function getAvailableDrivers()
+    public function getAvailableDrivers(): array
     {
         return $this->getDal()->getAvailableDrivers();
     }
 
     /**
      * Set attributes.
-     *
-     * @param   array  $attributes    Attributes values.
-     * @return  array
-     * @throws  \Hoa\Database\Exception
      */
-    public function setAttributes(array $attributes)
+    public function setAttributes(array $attributes): array
     {
         return $this->getDal()->setAttributes($attributes);
     }
 
     /**
      * Set a specific attribute.
-     *
-     * @param   mixed   $attribute    Attribute name.
-     * @param   mixed   $value        Attribute value.
-     * @return  mixed
-     * @throws  \Hoa\Database\Exception
      */
     public function setAttribute($attribute, $value)
     {
@@ -536,33 +458,24 @@ public function setAttribute($attribute, $value)
 
     /**
      * Retrieve all database connection attributes.
-     *
-     * @return  array
-     * @throws  \Hoa\Database\Exception
      */
-    public function getAttributes()
+    public function getAttributes(): array
     {
         return $this->getDal()->getAttributes();
     }
 
     /**
      * Retrieve a database connection attribute.
-     *
-     * @param   string  $attribute    Attribute name.
-     * @return  mixed
-     * @throws  \Hoa\Database\Exception
      */
-    public function getAttribute($attribute)
+    public function getAttribute(string $attribute)
     {
         return $this->getDal()->getAttribute($attribute);
     }
 
     /**
      * Get current ID.
-     *
-     * @return  string
      */
-    public function getId()
+    public function getId(): string
     {
         return $this->__id;
     }
diff --git a/DalStatement.php b/Source/DalStatement.php
similarity index 71%
rename from DalStatement.php
rename to Source/DalStatement.php
index 4da82f3..284b674 100644
--- a/DalStatement.php
+++ b/Source/DalStatement.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * Hoa
  *
@@ -40,9 +42,6 @@
  * Class \Hoa\Database\DalStatement.
  *
  * The higher class that represents a DAL statement.
- *
- * @copyright  Copyright © 2007-2017 Hoa community
- * @license    New BSD License
  */
 class DalStatement implements IDal\WrapperStatement
 {
@@ -185,7 +184,7 @@ class DalStatement implements IDal\WrapperStatement
     /**
      * The statement instance.
      *
-     * @var \Hoa\Database\IDal\WrapperStatement
+     * @var IDal\WrapperStatement
      */
     protected $statement = null;
 
@@ -193,10 +192,6 @@ class DalStatement implements IDal\WrapperStatement
 
     /**
      * Create a statement instance.
-     *
-     * @param   \Hoa\Database\IDal\WrapperStatement  $statement    The
-     *                                                             statement
-     *                                                             instance.
      */
     public function __construct(IDal\WrapperStatement $statement)
     {
@@ -207,13 +202,8 @@ public function __construct(IDal\WrapperStatement $statement)
 
     /**
      * Set the statement instance.
-     *
-     * @param   \Hoa\Database\IDal\WrapperStatement  $statement    The
-     *                                                             statement
-     *                                                             instance.
-     * @return  \Hoa\Database\IDal\WrapperStatement
      */
-    protected function setStatement(IDal\WrapperStatement $statement)
+    protected function setStatement(IDal\WrapperStatement $statement): ?IDal\WrapperStatement
     {
         $old             = $this->statement;
         $this->statement = $statement;
@@ -223,23 +213,16 @@ protected function setStatement(IDal\WrapperStatement $statement)
 
     /**
      * Get the statement instance.
-     *
-     * @return  \Hoa\Database\IDal\WrapperStatement
      */
-    protected function getStatement()
+    protected function getStatement(): IDal\WrapperStatement
     {
         return $this->statement;
     }
 
     /**
      * Execute a prepared statement.
-     *
-     * @param   array   $bindParameters    Bind parameters values if bindParam is
-     *                                     not called.
-     * @return  \Hoa\Database\DalStatement
-     * @throws  \Hoa\Database\Exception
      */
-    public function execute(array $bindParameters = [])
+    public function execute(array $bindParameters = []): self
     {
         if (empty($bindParameters)) {
             return $this->getStatement()->execute();
@@ -252,20 +235,13 @@ public function execute(array $bindParameters = [])
 
     /**
      * Bind a parameter to te specified variable name.
-     *
-     * @param   mixed   $parameter    Parameter name.
-     * @param   mixed   $value        Parameter value.
-     * @param   int     $type         Type of value.
-     * @param   int     $length       Length of data type.
-     * @return  bool
-     * @throws  \Hoa\Database\Exception
      */
     public function bindParameter(
         $parameter,
         &$value,
-        $type = null,
-        $length = null
-    ) {
+        ?int $type   = null,
+        int  $length = null
+    ) : bool {
         if (null === $type) {
             return $this->getStatement()->bindParameter($parameter, $value);
         }
@@ -288,37 +264,22 @@ public function bindParameter(
 
     /**
      * Return an array containing all of the result set rows.
-     *
-     * @return  array
-     * @throws  \Hoa\Database\Exception
      */
-    public function fetchAll()
+    public function fetchAll(): array
     {
         return $this->getStatement()->fetchAll();
     }
 
     /**
      * Set the iterator fetching style.
-     *
-     * @param   int    $offset         This value must be one of the
-     *                                 DalStatement::FROM_* constants or an
-     *                                 arbitrary offset.
-     * @param   int    $orientation    This value must be DalStatement::FORWARD
-     *                                 or DalStatement::BACKWARD constant.
-     * @param   int    $style          This value must be one of the
-     *                                 DalStatement::AS_* constants.
-     * @param   mixed  $arg1           For AS_CLASS: The class name.
-     *                                 For AS_REUSABLE_OBJECT: An object.
-     * @param   array  $arg2           For AS_CLASS: Constructor arguments.
-     * @return  \Hoa\Database\DalStatement
      */
     public function setFetchingStyle(
-        $offset      = self::FROM_START,
-        $orientation = self::FORWARD,
-        $style       = self::AS_MAP,
-        $arg1        = null,
-        $arg2        = null
-    ) {
+        int $offset      = self::FROM_START,
+        int $orientation = self::FORWARD,
+        int $style       = self::AS_MAP,
+        $arg1            = null,
+        array $arg2      = null
+    ): self {
         $this->getStatement()->setFetchingStyle(
             $offset,
             $orientation,
@@ -332,32 +293,24 @@ public function setFetchingStyle(
 
     /**
      * Get an Iterator.
-     *
-     * @return  \Hoa\Database\IDal\WrapperIterator
      */
-    public function getIterator()
+    public function getIterator(): IDal\WrapperIterator
     {
         return $this->getStatement()->getIterator();
     }
 
     /**
      * Fetch the first row in the result set.
-     *
-     * @param   int  $style    Must be one of the DalStatement::AS_* constants.
-     * @return  mixed
      */
-    public function fetchFirst($style = null)
+    public function fetchFirst(int $style = null)
     {
         return $this->getStatement()->fetchFirst($style);
     }
 
     /**
      * Fetch the last row in the result set.
-     *
-     * @param   int  $style    Must be one of the DalStatement::AS_* constants.
-     * @return  mixed
      */
-    public function fetchLast($style = null)
+    public function fetchLast(int $style = null)
     {
         return $this->getStatement()->fetchLast($style);
     }
@@ -365,23 +318,16 @@ public function fetchLast($style = null)
     /**
      * Return a single column from the next row of the result set or false if
      * there is no more row.
-     *
-     * @param   int  $column    Column index.
-     * @return  mixed
-     * @throws  \Hoa\Database\Exception
      */
-    public function fetchColumn($column = 0)
+    public function fetchColumn(int $column = 0)
     {
         return $this->getStatement()->fetchColumn($column);
     }
 
     /**
      * Close the cursor, enabling the statement to be executed again.
-     *
-     * @return  bool
-     * @throws  \Hoa\Database\Exception
      */
-    public function closeCursor()
+    public function closeCursor(): bool
     {
         return $this->getStatement()->closeCursor();
     }
@@ -389,11 +335,8 @@ public function closeCursor()
     /**
      * Fetch the SQLSTATE associated with the last operation on the statement
      * handle.
-     *
-     * @return  string
-     * @throws  \Hoa\Database\Exception
      */
-    public function errorCode()
+    public function errorCode(): string
     {
         return $this->getStatement()->errorCode();
     }
@@ -401,11 +344,8 @@ public function errorCode()
     /**
      * Fetch extends error information associated with the last operation on the
      * statement handle.
-     *
-     * @return  array
-     * @throws  \Hoa\Database\Exception
      */
-    public function errorInfo()
+    public function errorInfo(): array
     {
         return $this->getStatement()->errorInfo();
     }
diff --git a/Exception.php b/Source/Exception.php
similarity index 95%
rename from Exception.php
rename to Source/Exception.php
index b20918b..4df96fd 100644
--- a/Exception.php
+++ b/Source/Exception.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * Hoa
  *
@@ -42,9 +44,6 @@
  * Class \Hoa\Database\Exception.
  *
  * Extending the \Hoa\Exception\Exception class.
- *
- * @copyright  Copyright © 2007-2017 Hoa community
- * @license    New BSD License
  */
 class Exception extends HoaException
 {
diff --git a/IDal/Wrapper.php b/Source/IDal/Wrapper.php
similarity index 50%
rename from IDal/Wrapper.php
rename to Source/IDal/Wrapper.php
index 2024ee7..904d17b 100644
--- a/IDal/Wrapper.php
+++ b/Source/IDal/Wrapper.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * Hoa
  *
@@ -40,154 +42,89 @@
  * Interface \Hoa\Database\IDal\Wrapper.
  *
  * Interface of a DAL wrapper.
- *
- * @copyright  Copyright © 2007-2017 Hoa community
- * @license    New BSD License
  */
 interface Wrapper
 {
     /**
      * Create a DAL instance, representing a connection to a database.
-     *
-     * @param   string  $dsn              The DSN of database.
-     * @param   string  $username         The username to connect to database.
-     * @param   string  $password         The password to connect to database.
-     * @param   array   $driverOptions    The driver options.
-     * @throws  \Hoa\Database\Exception
      */
     public function __construct(
-        $dsn,
-        $username,
-        $password,
+        string $dsn,
+        string $username,
+        string $password,
         array $driverOptions = []
     );
 
     /**
      * Initiate a transaction.
-     *
-     * @return  bool
-     * @throws  \Hoa\Database\Exception
      */
-    public function beginTransaction();
+    public function beginTransaction(): bool;
 
     /**
      * Commit a transaction.
-     *
-     * @return  bool
-     * @throws  \Hoa\Database\Exception
      */
-    public function commit();
+    public function commit(): bool;
 
     /**
      * Roll back a transaction.
-     *
-     * @return  bool
-     * @throws  \Hoa\Database\Exception
      */
-    public function rollBack();
+    public function rollBack(): bool;
 
     /**
      * Return the ID of the last inserted row or sequence value.
-     *
-     * @param   string  $name    Name of sequence object (needed for some
-     *                           driver).
-     * @return  string
-     * @throws  \Hoa\Database\Exception
      */
-    public function lastInsertId($name = null);
+    public function lastInsertId(string $name = null): string;
 
     /**
      * Prepare a statement for execution and returns a statement object.
-     *
-     * @param   string  $statement    This must be a valid SQL statement for the
-     *                                target database server.
-     * @param   array   $options      Options to set attributes values for the
-     *                                AbstractLayer Statement.
-     * @return  \Hoa\Database\IDal\WrapperStatement
-     * @throws  \Hoa\Database\Exception
      */
-    public function prepare($statement, array $options = []);
+    public function prepare(string $statement, array $options = []): WrapperStatement;
 
     /**
      * Quote a string for use in a query.
-     *
-     * @param   string  $string    The string to be quoted.
-     * @param   int     $type      Provide a data type hint for drivers that
-     *                             have alternate quoting styles.
-     * @return  string
-     * @throws  \Hoa\Database\Exception
      */
-    public function quote($string = null, $type = -1);
+    public function quote(?string $string, int $type = -1): string;
 
     /**
      * Execute an SQL statement, returning a result set as a
      * \Hoa\Database\IDal\WrapperStatement object.
-     *
-     * @param   string  $statement    The SQL statement to prepare and execute.
-     * @return  \Hoa\Database\IDal\WrapperStatement
-     * @throws  \Hoa\Database\Exception
      */
-    public function query($statement);
+    public function query(string $statement): WrapperStatement;
 
     /**
      * Fetch the SQLSTATE associated with the last operation on the database
      * handle.
-     *
-     * @return  string
-     * @throws  \Hoa\Database\Exception
      */
-    public function errorCode();
+    public function errorCode(): string;
 
     /**
      * Fetch extends error information associated with the last operation on the
      * database handle.
-     *
-     * @return  array
-     * @throws  \Hoa\Database\Exception
      */
-    public function errorInfo();
+    public function errorInfo(): array;
 
     /**
      * Return an array of available drivers.
-     *
-     * @return  array
-     * @throws  \Hoa\Database\Exception
      */
-    public function getAvailableDrivers();
+    public function getAvailableDrivers(): array;
 
     /**
      * Set attributes.
-     *
-     * @param   array   $attributes    Attributes values.
-     * @return  array
-     * @throws  \Hoa\Database\Exception
      */
-    public function setAttributes(array $attributes);
+    public function setAttributes(array $attributes): array;
 
     /**
      * Set a specific attribute.
-     *
-     * @param   mixed   $attribute    Attribute name.
-     * @param   mixed   $value        Attribute value.
-     * @return  mixed
-     * @throws  \Hoa\Database\Exception
      */
     public function setAttribute($attribute, $value);
 
     /**
      * Retrieve all database connection attributes.
-     *
-     * @return  array
-     * @throws  \Hoa\Database\Exception
      */
-    public function getAttributes();
+    public function getAttributes(): array;
 
     /**
      * Retrieve a database connection attribute.
-     *
-     * @param   string  $attribute    Attribute name.
-     * @return  mixed
-     * @throws  \Hoa\Database\Exception
      */
-    public function getAttribute($attribute);
+    public function getAttribute(string $attribute);
 }
diff --git a/IDal/WrapperIterator.php b/Source/IDal/WrapperIterator.php
similarity index 86%
rename from IDal/WrapperIterator.php
rename to Source/IDal/WrapperIterator.php
index fd24646..355b6e1 100644
--- a/IDal/WrapperIterator.php
+++ b/Source/IDal/WrapperIterator.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * Hoa
  *
@@ -42,17 +44,11 @@
  * Interface \Hoa\Database\IDal\WrapperIterator.
  *
  * Interface of a DAL iterator statement wrapper.
- *
- * @copyright  Copyright © 2007-2017 Hoa community
- * @license    New BSD License
  */
 interface WrapperIterator extends Iterator\Iterator
 {
     /**
      * Create an iterator instance.
-     *
-     * @param   object  $statement    The underlying statement instance.
-     * @param   array   $style        An array of fetching style options.
      */
-    public function __construct($statement, $style);
+    public function __construct($statement, array $style);
 }
diff --git a/IDal/WrapperStatement.php b/Source/IDal/WrapperStatement.php
similarity index 52%
rename from IDal/WrapperStatement.php
rename to Source/IDal/WrapperStatement.php
index 3250dab..7eac37b 100644
--- a/IDal/WrapperStatement.php
+++ b/Source/IDal/WrapperStatement.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * Hoa
  *
@@ -43,119 +45,70 @@
  * Interface \Hoa\Database\IDal\WrapperStatement.
  *
  * Interface of a DAL statement wrapper.
- *
- * @copyright  Copyright © 2007-2017 Hoa community
- * @license    New BSD License
  */
 interface WrapperStatement extends Iterator\Aggregate
 {
     /**
      * Execute a prepared statement.
-     *
-     * @param   array   $bindParameters    Bind parameters values if
-     *                                     bindParameter() is not called.
-     * @return  \Hoa\Database\IDal\WrapperStatement
-     * @throws  \Hoa\Database\Exception
      */
-    public function execute(array $bindParameters = []);
+    public function execute(array $bindParameters = []): WrapperStatement;
 
     /**
      * Bind a parameter to te specified variable name.
-     *
-     * @param   mixed   $parameter    Parameter name.
-     * @param   mixed   $value        Parameter value.
-     * @param   int     $type         Type of value.
-     * @param   int     $length       Length of data type.
-     * @return  bool
-     * @throws  \Hoa\Database\Exception
      */
     public function bindParameter(
         $parameter,
         &$value,
-        $type   = null,
-        $length = null
-    );
+        ?int $type   = null,
+        int  $length = null
+    ): bool;
 
     /**
      * Return an array containing all of the result set rows.
-     *
-     * @return  array
-     * @throws  \Hoa\Database\Exception
      */
-    public function fetchAll();
+    public function fetchAll(): array;
 
     /**
      * Set the Iterator fetching style.
-     *
-     * @param   int    $offset         This value must be one of the
-     *                                 DalStatement::FROM_* constants or an
-     *                                 arbitrary offset.
-     * @param   int    $orientation    This value must be DalStatement::FORWARD
-     *                                 or DalStatement::BACKWARD constant.
-     * @param   int    $style          This value must be one of the
-     *                                 DalStatement::AS_* constants.
-     * @param   mixed  $arg1           For AS_CLASS: The Class name.
-     *                                 For AS_REUSABLE_OBJECT: An object.
-     * @param   array  $arg2           For AS_CLASS: Constructor arguments.
-     * @return  \Hoa\Database\IDal\WrapperStatement
      */
     public function setFetchingStyle(
-        $offset      = Database\DalStatement::FROM_START,
-        $orientation = Database\DalStatement::FORWARD,
-        $style       = Database\DalStatement::AS_MAP,
-        $arg1        = null,
-        $arg2        = null
-    );
+        int $offset      = Database\DalStatement::FROM_START,
+        int $orientation = Database\DalStatement::FORWARD,
+        int $style       = Database\DalStatement::AS_MAP,
+        $arg1            = null,
+        array $arg2      = null
+    ) : WrapperStatement;
 
     /**
      * Fetch the first row in the result set.
-     *
-     * @param   int  $style    Must be one of the DalStatement::AS_* constants.
-     * @return  mixed
      */
-    public function fetchFirst($style = null);
+    public function fetchFirst(int $style = null);
 
     /**
      * Fetch the last row in the result set.
-     *
-     * @param   int  $style    Must be one of the DalStatement::AS_* constants.
-     * @return  mixed
      */
-    public function fetchLast($style = null);
+    public function fetchLast(int $style = null);
 
     /**
      * Return a single column from the next row of the result set or false if
      * there is no more row.
-     *
-     * @param   int  $column    Column index.
-     * @return  mixed
-     * @throws  \Hoa\Database\Exception
      */
-    public function fetchColumn($column = 0);
+    public function fetchColumn(int $column = 0);
 
     /**
      * Close the cursor, enabling the statement to be executed again.
-     *
-     * @return  bool
-     * @throws  \Hoa\Database\Exception
      */
-    public function closeCursor();
+    public function closeCursor(): bool;
 
     /**
      * Fetch the SQLSTATE associated with the last operation on the statement
      * handle.
-     *
-     * @return  string
-     * @throws  \Hoa\Database\Exception
      */
-    public function errorCode();
+    public function errorCode(): string;
 
     /**
      * Fetch extends error information associated with the last operation on the
      * statement handle.
-     *
-     * @return  array
-     * @throws  \Hoa\Database\Exception
      */
-    public function errorInfo();
+    public function errorInfo(): array;
 }
diff --git a/Layer/Dba/Dba.php b/Source/Layer/Dba/Dba.php
similarity index 100%
rename from Layer/Dba/Dba.php
rename to Source/Layer/Dba/Dba.php
diff --git a/Layer/Dba/DbaStatement.php b/Source/Layer/Dba/DbaStatement.php
similarity index 100%
rename from Layer/Dba/DbaStatement.php
rename to Source/Layer/Dba/DbaStatement.php
diff --git a/Layer/Dbx/Dbx.php b/Source/Layer/Dbx/Dbx.php
similarity index 100%
rename from Layer/Dbx/Dbx.php
rename to Source/Layer/Dbx/Dbx.php
diff --git a/Layer/Dbx/DbxStatement.php b/Source/Layer/Dbx/DbxStatement.php
similarity index 100%
rename from Layer/Dbx/DbxStatement.php
rename to Source/Layer/Dbx/DbxStatement.php
diff --git a/Layer/Odbc/Odbc.php b/Source/Layer/Odbc/Odbc.php
similarity index 100%
rename from Layer/Odbc/Odbc.php
rename to Source/Layer/Odbc/Odbc.php
diff --git a/Layer/Odbc/OdbcStatement.php b/Source/Layer/Odbc/OdbcStatement.php
similarity index 100%
rename from Layer/Odbc/OdbcStatement.php
rename to Source/Layer/Odbc/OdbcStatement.php
diff --git a/Layer/Pdo/Iterator.php b/Source/Layer/Pdo/Iterator.php
similarity index 88%
rename from Layer/Pdo/Iterator.php
rename to Source/Layer/Pdo/Iterator.php
index 3ee3800..28ab809 100644
--- a/Layer/Pdo/Iterator.php
+++ b/Source/Layer/Pdo/Iterator.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * Hoa
  *
@@ -42,9 +44,6 @@
  * Class \Hoa\Database\Layer\Pdo\Iterator.
  *
  * Iterator Statement.
- *
- * @copyright  Copyright © 2007-2017 Hoa community
- * @license    New BSD License
  */
 class Iterator implements Database\IDal\WrapperIterator
 {
@@ -73,11 +72,8 @@ class Iterator implements Database\IDal\WrapperIterator
 
     /**
      * Create an iterator instance.
-     *
-     * @param   object  $statement    The underlying statement instance.
-     * @param   array   $style        An array of fetching style options.
      */
-    public function __construct($statement, $style)
+    public function __construct(\PDOStatement $statement, array $style)
     {
         $this->_statement = $statement;
         $this->_style     = $style;
@@ -111,28 +107,22 @@ public function __construct($statement, $style)
 
     /**
      * Get the statement instance.
-     *
-     * @return  \PDOStatement
      */
-    protected function getStatement()
+    protected function getStatement(): \PDOStatement
     {
         return $this->_statement;
     }
 
     /**
      * Return the current element.
-     *
-     * @return  array
      */
-    public function current()
+    public function current(): array
     {
         return $this->_row;
     }
 
     /**
      * Move forward to next element.
-     *
-     * @return  void
      */
     public function next()
     {
@@ -146,8 +136,6 @@ public function next()
 
     /**
      * Return always null.
-     *
-     * @return  null
      */
     public function key()
     {
@@ -156,18 +144,14 @@ public function key()
 
     /**
      * Checks if current position is valid.
-     *
-     * @return  bool
      */
-    public function valid()
+    public function valid() : bool
     {
         return false !== $this->_row;
     }
 
     /**
      * Rewind the iterator to the first element.
-     *
-     * @return  void
      */
     public function rewind()
     {
diff --git a/Layer/Pdo/Pdo.php b/Source/Layer/Pdo/Pdo.php
similarity index 68%
rename from Layer/Pdo/Pdo.php
rename to Source/Layer/Pdo/Pdo.php
index afdae5d..1812686 100644
--- a/Layer/Pdo/Pdo.php
+++ b/Source/Layer/Pdo/Pdo.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * Hoa
  *
@@ -43,9 +45,6 @@
  * Class \Hoa\Database\Layer\Pdo.
  *
  * Wrap PDO.
- *
- * @copyright  Copyright © 2007-2017 Hoa community
- * @license    New BSD License
  */
 class Pdo implements Database\IDal\Wrapper
 {
@@ -60,17 +59,11 @@ class Pdo implements Database\IDal\Wrapper
 
     /**
      * Create a DAL instance, representing a connection to a database.
-     *
-     * @param   string  $dsn              The DSN of database.
-     * @param   string  $username         The username to connect to database.
-     * @param   string  $password         The password to connect to database.
-     * @param   array   $driverOptions    The driver options.
-     * @throws  \Hoa\Database\Exception
      */
     public function __construct(
-        $dsn,
-        $username,
-        $password,
+        string $dsn,
+        string $username,
+        string $password,
         array $driverOptions = []
     ) {
         if (false === extension_loaded('pdo')) {
@@ -100,11 +93,8 @@ public function __construct(
 
     /**
      * Set the connection.
-     *
-     * @param   \PDO        $connection    The PDO instance.
-     * @return  \PDO
      */
-    protected function setConnection(\PDO $connection)
+    protected function setConnection(\PDO $connection): \PDO
     {
         $old               = $this->_connection;
         $this->_connection = $connection;
@@ -114,11 +104,8 @@ protected function setConnection(\PDO $connection)
 
     /**
      * Get the connection instance.
-     *
-     * @return  \PDO
-     * @throws  \Hoa\Database\Exception
      */
-    protected function getConnection()
+    protected function getConnection(): \PDO
     {
         if (null === $this->_connection) {
             throw new Database\Exception(
@@ -132,46 +119,32 @@ protected function getConnection()
 
     /**
      * Initiate a transaction.
-     *
-     * @return  bool
-     * @throws  \Hoa\Database\Exception
      */
-    public function beginTransaction()
+    public function beginTransaction(): bool
     {
         return $this->getConnection()->beginTransaction();
     }
 
     /**
      * Commit a transaction.
-     *
-     * @return  bool
-     * @throws  \Hoa\Database\Exception
      */
-    public function commit()
+    public function commit(): bool
     {
         return $this->getConnection()->commit();
     }
 
     /**
      * Roll back a transaction.
-     *
-     * @return  bool
-     * @throws  \Hoa\Database\Exception
      */
-    public function rollBack()
+    public function rollBack(): bool
     {
         return $this->getConnection()->rollBack();
     }
 
     /**
      * Return the ID of the last inserted row or sequence value.
-     *
-     * @param   string  $name    Name of sequence object (needed for some
-     *                           driver).
-     * @return  string
-     * @throws  \Hoa\Database\Exception
      */
-    public function lastInsertId($name = null)
+    public function lastInsertId(string $name = null): string
     {
         if (null === $name) {
             return $this->getConnection()->lastInsertId();
@@ -182,15 +155,8 @@ public function lastInsertId($name = null)
 
     /**
      * Prepare a statement for execution and returns a statement object.
-     *
-     * @param   string  $statement    This must be a valid SQL statement for the
-     *                                target database server.
-     * @param   array   $options      Options to set attributes values for the
-     *                                Layer Statement.
-     * @return  \Hoa\Database\Layer\Pdo\Statement
-     * @throws  \Hoa\Database\Exception
      */
-    public function prepare($statement, array $options = [])
+    public function prepare(string $statement, array $options = []): Database\IDal\WrapperStatement
     {
         if (!isset($options[\PDO::ATTR_CURSOR])) {
             try {
@@ -217,14 +183,8 @@ public function prepare($statement, array $options = [])
 
     /**
      * Quote a sting for use in a query.
-     *
-     * @param   string  $string    The string to be quoted.
-     * @param   int     $type      Provide a data type hint for drivers that
-     *                             have alternate quoting styles.
-     * @return  string
-     * @throws  \Hoa\Database\Exception
      */
-    public function quote($string = null, $type = -1)
+    public function quote(?string $string, int $type = -1): string
     {
         if ($type < 0) {
             return $this->getConnection()->quote($string);
@@ -236,12 +196,8 @@ public function quote($string = null, $type = -1)
     /**
      * Execute an SQL statement, returning a result set as a
      * \Hoa\Database\Layer\Pdo\Statement object.
-     *
-     * @param   string  $statement    The SQL statement to prepare and execute.
-     * @return  \Hoa\Database\Layer\Pdo\Statement
-     * @throws  \Hoa\Database\Exception
      */
-    public function query($statement)
+    public function query(string $statement): Database\IDal\WrapperStatement
     {
         $handle = $this->getConnection()->query($statement);
 
@@ -259,11 +215,8 @@ public function query($statement)
     /**
      * Fetch the SQLSTATE associated with the last operation on the database
      * handle.
-     *
-     * @return  string
-     * @throws  \Hoa\Database\Exception
      */
-    public function errorCode()
+    public function errorCode(): string
     {
         return $this->getConnection()->errorCode();
     }
@@ -271,34 +224,24 @@ public function errorCode()
     /**
      * Fetch extends error information associated with the last operation on the
      * database handle.
-     *
-     * @return  array
-     * @throws  \Hoa\Database\Exception
      */
-    public function errorInfo()
+    public function errorInfo(): array
     {
         return $this->getConnection()->errorInfo();
     }
 
     /**
      * Return an array of available drivers.
-     *
-     * @return  array
-     * @throws  \Hoa\Database\Exception
      */
-    public function getAvailableDrivers()
+    public function getAvailableDrivers(): array
     {
         return $this->getConnection()->getAvailableDrivers();
     }
 
     /**
      * Set attributes.
-     *
-     * @param   array   $attributes    Attributes values.
-     * @return  array
-     * @throws  \Hoa\Database\Exception
      */
-    public function setAttributes(array $attributes)
+    public function setAttributes(array $attributes): array
     {
         $out = true;
 
@@ -311,11 +254,6 @@ public function setAttributes(array $attributes)
 
     /**
      * Set a specific attribute.
-     *
-     * @param   mixed   $attribute    Attribute name.
-     * @param   mixed   $value        Attribute value.
-     * @return  mixed
-     * @throws  \Hoa\Database\Exception
      */
     public function setAttribute($attribute, $value)
     {
@@ -324,11 +262,8 @@ public function setAttribute($attribute, $value)
 
     /**
      * Retrieve all database connection attributes.
-     *
-     * @return  array
-     * @throws  \Hoa\Database\Exception
      */
-    public function getAttributes()
+    public function getAttributes(): array
     {
         $out        = [];
         $attributes = [
@@ -355,12 +290,8 @@ public function getAttributes()
 
     /**
      * Retrieve a database connection attribute.
-     *
-     * @param   string  $attribute    Attribute name.
-     * @return  mixed
-     * @throws  \Hoa\Database\Exception
      */
-    public function getAttribute($attribute)
+    public function getAttribute(string $attribute)
     {
         return
             $this
@@ -372,4 +303,4 @@ public function getAttribute($attribute)
 /**
  * Flex entity.
  */
-Consistency::flexEntity('Hoa\Database\Layer\Pdo\Pdo');
+Consistency::flexEntity(Pdo::class);
diff --git a/Layer/Pdo/Statement.php b/Source/Layer/Pdo/Statement.php
similarity index 63%
rename from Layer/Pdo/Statement.php
rename to Source/Layer/Pdo/Statement.php
index 72b5997..c54a4b7 100644
--- a/Layer/Pdo/Statement.php
+++ b/Source/Layer/Pdo/Statement.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * Hoa
  *
@@ -42,9 +44,6 @@
  * Class \Hoa\Database\Layer\Pdo\Statement.
  *
  * Wrap PDOStatement.
- *
- * @copyright  Copyright © 2007-2017 Hoa community
- * @license    New BSD License
  */
 class Statement implements Database\IDal\WrapperStatement
 {
@@ -70,8 +69,6 @@ class Statement implements Database\IDal\WrapperStatement
 
     /**
      * Create a statement instance.
-     *
-     * @param   \PDOStatement  $statement    The PDOStatement instance.
      */
     public function __construct(\PDOStatement $statement)
     {
@@ -82,11 +79,8 @@ public function __construct(\PDOStatement $statement)
 
     /**
      * Set the statement instance.
-     *
-     * @param   \PDOStatement  $statement    The PDOStatement instance.
-     * @return  \PDOStatement
      */
-    protected function setStatement(\PDOStatement $statement)
+    protected function setStatement(\PDOStatement $statement): \PDOStatement
     {
         $old              = $this->_statement;
         $this->_statement = $statement;
@@ -96,23 +90,16 @@ protected function setStatement(\PDOStatement $statement)
 
     /**
      * Get the statement instance.
-     *
-     * @return  \PDOStatement
      */
-    protected function getStatement()
+    protected function getStatement(): \PDOStatement
     {
         return $this->_statement;
     }
 
     /**
      * Execute a prepared statement.
-     *
-     * @param   array   $bindParameters    Bind parameters values if bindParam
-     *                                     is not called.
-     * @return  \Hoa\Database\Layer\Pdo\Statement
-     * @throws  \Hoa\Database\Exception
      */
-    public function execute(array $bindParameters = null)
+    public function execute(array $bindParameters = null): Database\IDal\WrapperStatement
     {
         if (false === $this->getStatement()->execute($bindParameters)) {
             throw new Database\Exception(
@@ -127,20 +114,13 @@ public function execute(array $bindParameters = null)
 
     /**
      * Bind a parameter to te specified variable name.
-     *
-     * @param   mixed   $parameter    Parameter name.
-     * @param   mixed   $value        Parameter value.
-     * @param   int     $type         Type of value.
-     * @param   int     $length       Length of data type.
-     * @return  bool
-     * @throws  \Hoa\Database\Exception
      */
     public function bindParameter(
         $parameter,
         &$value,
-        $type = null,
-        $length = null
-    ) {
+        ?int $type  = null,
+        int $length = null
+    ): bool {
         if (null === $type) {
             return $this->getStatement()->bindParam($parameter, $value);
         }
@@ -154,26 +134,14 @@ public function bindParameter(
 
     /**
      * Set the iterator fetching style.
-     *
-     * @param   int    $offset         This value must be one of the
-     *                                 DalStatement::FROM_* constants or an
-     *                                 arbitrary offset.
-     * @param   int    $orientation    This value must be DalStatement::FORWARD
-     *                                 or DalStatement::BACKWARD constant.
-     * @param   int    $style          This value must be one of the
-     *                                 DalStatement::AS_* constants.
-     * @param   mixed  $arg1           For AS_CLASS: The class name.
-     *                                 For AS_REUSABLE_OBJECT: An object.
-     * @param   array  $arg2           For AS_CLASS: Constructor arguments.
-     * @return  \Hoa\Database\Layer\Pdo\Statement
      */
     public function setFetchingStyle(
-        $offset      = Database\DalStatement::FROM_START,
-        $orientation = Database\DalStatement::FORWARD,
-        $style       = Database\DalStatement::AS_MAP,
-        $arg1        = null,
-        $arg2        = null
-    ) {
+        int $offset      = Database\DalStatement::FROM_START,
+        int $orientation = Database\DalStatement::FORWARD,
+        int $style       = Database\DalStatement::AS_MAP,
+        $arg1            = null,
+        array $arg2      = null
+    ): Database\IDal\WrapperStatement {
         $this->_style[Database\DalStatement::STYLE_OFFSET]      = $offset;
         $this->_style[Database\DalStatement::STYLE_ORIENTATION] = $orientation;
         $this->_style[Database\DalStatement::STYLE_MODE]        = $style;
@@ -190,10 +158,8 @@ public function setFetchingStyle(
 
     /**
      * Get an Iterator.
-     *
-     * @return  \Hoa\Database\Layer\Pdo\Iterator
      */
-    public function getIterator()
+    public function getIterator(): Iterator
     {
         return new Iterator(
             $this->getStatement(),
@@ -203,47 +169,32 @@ public function getIterator()
 
     /**
      * Return an array containing all of the result set rows.
-     *
-     * @return  array
-     * @throws  \Hoa\Database\Exception
      */
-    public function fetchAll()
+    public function fetchAll(): array
     {
         return $this->getStatement()->fetchAll(\PDO::FETCH_ASSOC);
     }
 
     /**
      * Fetch the first row in the result set.
-     *
-     * @param   int  $style    Must be one of the DalStatement::AS_* constants.
-     * @return  mixed
      */
-    public function fetchFirst($style = null)
+    public function fetchFirst(int $style = null)
     {
         return $this->fetch($style, \PDO::FETCH_ORI_FIRST);
     }
 
     /**
      * Fetch the last row in the result set.
-     *
-     * @param   int  $style    Must be one of the DalStatement::AS_* constants.
-     * @return  mixed
      */
-    public function fetchLast($style = null)
+    public function fetchLast(int $style = null)
     {
         return $this->fetch($style, \PDO::FETCH_ORI_LAST);
     }
 
     /**
      * Fetch a row in the result set.
-     *
-     * @param   int  $style          Must be one of the DalStatement::AS_*
-     *                               constants.
-     * @param   int  $orientation    Must be one of the \PDO::FETCH_ORI_*
-     *                               constants.
-     * @return  mixed
      */
-    protected function fetch($style, $orientation)
+    protected function fetch(int $style, int $orientation)
     {
         return $this->getStatement()->fetch(
             $style ?: $this->_style,
@@ -254,23 +205,16 @@ protected function fetch($style, $orientation)
     /**
      * Return a single column from the next row of the result set or false if
      * there is no more row.
-     *
-     * @param   int  $column    Column index.
-     * @return  mixed
-     * @throws  \Hoa\Database\Exception
      */
-    public function fetchColumn($column = 0)
+    public function fetchColumn(int $column = 0)
     {
         return $this->getStatement()->fetchColumn($column);
     }
 
     /**
      * Close the cursor, enabling the statement to be executed again.
-     *
-     * @return  bool
-     * @throws  \Hoa\Database\Exception
      */
-    public function closeCursor()
+    public function closeCursor(): bool
     {
         return $this->getStatement()->closeCursor();
     }
@@ -278,11 +222,8 @@ public function closeCursor()
     /**
      * Fetch the SQLSTATE associated with the last operation on the statement
      * handle.
-     *
-     * @return  string
-     * @throws  \Hoa\Database\Exception
      */
-    public function errorCode()
+    public function errorCode(): string
     {
         return $this->getStatement()->errorCode();
     }
@@ -290,11 +231,8 @@ public function errorCode()
     /**
      * Fetch extends error information associated with the last operation on the
      * statement handle.
-     *
-     * @return  array
-     * @throws  \Hoa\Database\Exception
      */
-    public function errorInfo()
+    public function errorInfo(): array
     {
         return $this->getStatement()->errorInfo();
     }
diff --git a/Query/Delete.php b/Source/Query/Delete.php
similarity index 87%
rename from Query/Delete.php
rename to Source/Query/Delete.php
index eb17384..5a7aa85 100644
--- a/Query/Delete.php
+++ b/Source/Query/Delete.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * Hoa
  *
@@ -40,9 +42,6 @@
  * Class \Hoa\Database\Query\Delete.
  *
  * Build a DELETE query.
- *
- * @copyright  Copyright © 2007-2017 Hoa community
- * @license    New BSD License
  */
 class Delete extends Where implements Dml
 {
@@ -51,7 +50,7 @@ class Delete extends Where implements Dml
     /**
      * Table name.
      *
-     * @var string
+     * @var ?string
      */
     protected $_from = null;
 
@@ -59,11 +58,8 @@ class Delete extends Where implements Dml
 
     /**
      * Set the table name.
-     *
-     * @param   string  $source    Table name.
-     * @return  \Hoa\Database\Query\Delete
      */
-    public function from($source)
+    public function from(string $source): self
     {
         $this->_from = $source;
 
@@ -72,10 +68,8 @@ public function from($source)
 
     /**
      * Generate the query.
-     *
-     * @return  string
      */
-    public function __toString()
+    public function __toString(): string
     {
         return
             'DELETE FROM ' .
diff --git a/Query/Dml.php b/Source/Query/Dml.php
similarity index 78%
rename from Query/Dml.php
rename to Source/Query/Dml.php
index 9a471b3..021578b 100644
--- a/Query/Dml.php
+++ b/Source/Query/Dml.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * Hoa
  *
@@ -40,33 +42,21 @@
  * Interface \Hoa\Database\Query\Dml.
  *
  * Represent Data Manipulation Language queries.
- *
- * @copyright  Copyright © 2007-2017 Hoa community
- * @license    New BSD License
  */
 interface Dml
 {
     /**
      * Set enclose symbols.
-     *
-     * @param   string  $openingSymbol    Opening symbol.
-     * @param   string  $closingSymbol    Closing symbol.
-     * @return  \Hoa\Database\Query\Dml
      */
-    public function setEncloseSymbol($openingSymbol, $closingSymbol = null);
+    public function setEncloseSymbol(string $openingSymbol, string $closingSymbol = null): Dml;
 
     /**
      * Enable or disable enclosing identifiers.
-     *
-     * @param   bool  $enable    Enable or disable.
-     * @return  \Hoa\Database\Query\Dml
      */
-    public function enableEncloseIdentifier($enable = true);
+    public function enableEncloseIdentifier(bool $enable = true): bool;
 
     /**
      * Generate the query.
-     *
-     * @return  string
      */
-    public function __toString();
+    public function __toString(): string;
 }
diff --git a/Query/EncloseIdentifier.php b/Source/Query/EncloseIdentifier.php
similarity index 82%
rename from Query/EncloseIdentifier.php
rename to Source/Query/EncloseIdentifier.php
index b477a9c..189bd52 100644
--- a/Query/EncloseIdentifier.php
+++ b/Source/Query/EncloseIdentifier.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * Hoa
  *
@@ -40,9 +42,6 @@
  * Trait \Hoa\Database\Query\EncloseIdentifier.
  *
  * Enclose identifier feature.
- *
- * @copyright  Copyright © 2007-2017 Hoa community
- * @license    New BSD License
  */
 trait EncloseIdentifier
 {
@@ -72,12 +71,8 @@ trait EncloseIdentifier
 
     /**
      * Set enclose symbols.
-     *
-     * @param   string  $openingSymbol    Opening symbol.
-     * @param   string  $closingSymbol    Closing symbol.
-     * @return  \Hoa\Database\Query\EncloseIdentifier
      */
-    public function setEncloseSymbol($openingSymbol, $closingSymbol = null)
+    public function setEncloseSymbol(string $openingSymbol, string $closingSymbol = null): Dml
     {
         $this->_openingSymbol = $openingSymbol;
         $this->_closingSymbol = $closingSymbol ?: $openingSymbol;
@@ -87,11 +82,8 @@ public function setEncloseSymbol($openingSymbol, $closingSymbol = null)
 
     /**
      * Enable or disable enclosing identifiers.
-     *
-     * @param   bool  $enable    Enable or disable.
-     * @return  bool
      */
-    public function enableEncloseIdentifier($enable = true)
+    public function enableEncloseIdentifier(bool $enable = true): bool
     {
         $old                  = $this->_enableEnclose;
         $this->_enableEnclose = $enable;
@@ -101,9 +93,6 @@ public function enableEncloseIdentifier($enable = true)
 
     /**
      * Enclose identifiers with defined symbol.
-     *
-     * @param   array|string  $identifiers    Table/column/alias identifiers.
-     * @return  array|string
      */
     protected function enclose($identifiers)
     {
@@ -124,11 +113,8 @@ protected function enclose($identifiers)
 
     /**
      * Enclose identifier with defined symbol.
-     *
-     * @param   string  $identifier    Identifier.
-     * @return  string
      */
-    protected function _enclose($identifier)
+    protected function _enclose(string $identifier): string
     {
         if (0 === preg_match('#\s|\(#', $identifier)) {
             return $this->_openingSymbol . $identifier . $this->_closingSymbol;
diff --git a/Query/Insert.php b/Source/Query/Insert.php
similarity index 73%
rename from Query/Insert.php
rename to Source/Query/Insert.php
index 1a2c122..b34b3b7 100644
--- a/Query/Insert.php
+++ b/Source/Query/Insert.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * Hoa
  *
@@ -40,9 +42,6 @@
  * Class \Hoa\Database\Query\Insert.
  *
  * Build an INSERT query.
- *
- * @copyright  Copyright © 2007-2017 Hoa community
- * @license    New BSD License
  */
 class Insert implements Dml
 {
@@ -51,20 +50,20 @@ class Insert implements Dml
     /**
      * Source.
      *
-     * @var string
+     * @var ?string
      */
     protected $_into          = null;
 
     /**
      * Alternative to INSERT.
      *
-     * @var string
+     * @var ?string
      */
     protected $_or            = null;
 
     /**
      * Columns.
-     *
+    *
      * @var array
      */
     protected $_columns       = [];
@@ -72,9 +71,9 @@ class Insert implements Dml
     /**
      * Values (tuples).
      *
-     * @var array
+     * @var mixed
      */
-    protected $_values        = [];
+    protected $_values        = null;
 
     /**
      * Whether we should use default values or not.
@@ -87,11 +86,8 @@ class Insert implements Dml
 
     /**
      * Set source.
-     *
-     * @param   string  $name    Name.
-     * @return  \Hoa\Database\Query\Insert
      */
-    public function into($name)
+    public function into(string $name): self
     {
         $this->_into = $name;
 
@@ -100,61 +96,48 @@ public function into($name)
 
     /**
      * Insert or rollback.
-     *
-     * @return  \Hoa\Database\Query\Insert
      */
-    public function rollback()
+    public function rollback(): self
     {
         return $this->_or('ROLLBACK');
     }
 
     /**
      * Insert or abort.
-     *
-     * @return  \Hoa\Database\Query\Insert
      */
-    public function abort()
+    public function abort(): self
     {
         return $this->_or('ABORT');
     }
 
     /**
      * Insert or replace.
-     *
-     * @return  \Hoa\Database\Query\Insert
      */
-    public function replace()
+    public function replace(): self
     {
         return $this->_or('REPLACE');
     }
 
     /**
      * Insert or fail.
-     *
-     * @return  \Hoa\Database\Query\Insert
      */
-    public function fail()
+    public function fail(): self
     {
         return $this->_or('FAIL');
     }
 
     /**
      * Insert or ignore.
-     *
-     * @return  \Hoa\Database\Query\Insert
      */
-    public function ignore()
+    public function ignore(): self
     {
         return $this->_or('IGNORE');
     }
 
     /**
      * Declare an alternative to “INSERT”.
-     *
-     * @param   string  $or    Alternative.
-     * @return  \Hoa\Database\Query\Insert
      */
-    protected function _or($or)
+    protected function _or(string $or): self
     {
         $this->_or = $or;
 
@@ -163,14 +146,10 @@ protected function _or($or)
 
     /**
      * Set columns.
-     *
-     * @param   string  $column    Column name.
-     * @param   ...     ...
-     * @return  \Hoa\Database\Query\Insert
      */
-    public function on($column)
+    public function on(string ...$columns): self
     {
-        foreach (func_get_args() as $column) {
+        foreach ($columns as $column) {
             $this->_columns[] = $column;
         }
 
@@ -178,17 +157,13 @@ public function on($column)
     }
 
     /**
-     * Set values (on call per tuple).
+     * Set values (one call per tuple).
      * Expression can be: a regular value or a SELECT query.
-     *
-     * @param   mixed  $expression    Expression.
-     * @param   ...    ...
-     * @return  \Hoa\Database\Query\Insert
      */
-    public function values($expression)
+    public function values(...$expressions): self
     {
-        if ($expression instanceof Select) {
-            $this->_values = (string) $expression;
+        if (1 === count($expressions) && $expressions[0] instanceof Select) {
+            $this->_values = (string) $expressions[0];
         } else {
             if (is_string($this->_values)) {
                 $this->_values = [];
@@ -197,7 +172,7 @@ public function values($expression)
             $values = &$this->_values[];
             $values = [];
 
-            foreach (func_get_args() as $expression) {
+            foreach ($expressions as $expression) {
                 $values[] = $expression;
             }
         }
@@ -207,10 +182,8 @@ public function values($expression)
 
     /**
      * Use default values.
-     *
-     * @return  \Hoa\Database\Query\Insert
      */
-    public function defaultValues()
+    public function defaultValues(): self
     {
         $this->_defaultValues = true;
 
@@ -219,11 +192,8 @@ public function defaultValues()
 
     /**
      * Allow to use the “or” attribute to chain method calls.
-     *
-     * @param   string  $name    Name.
-     * @return  mixed
      */
-    public function __get($name)
+    public function __get(string $name)
     {
         switch (strtolower($name)) {
             case 'or':
@@ -236,10 +206,8 @@ public function __get($name)
 
     /**
      * Generate the query.
-     *
-     * @return  string
      */
-    public function __toString()
+    public function __toString(): string
     {
         $out = 'INSERT';
 
diff --git a/Query/Join.php b/Source/Query/Join.php
similarity index 77%
rename from Query/Join.php
rename to Source/Query/Join.php
index 1cdd07b..3388f5e 100644
--- a/Query/Join.php
+++ b/Source/Query/Join.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * Hoa
  *
@@ -40,23 +42,20 @@
  * Class \Hoa\Database\Query\Join.
  *
  * Build a JOIN clause.
- *
- * @copyright  Copyright © 2007-2017 Hoa community
- * @license    New BSD License
  */
 class Join
 {
     /**
      * Parent query.
      *
-     * @var \Hoa\Database\Query\Select
+     * @var ?Select
      */
     protected $_parent = null;
 
     /**
      * Reference the FROM entry of the parent (simulate “friends”).
      *
-     * @var string
+     * @var array
      */
     protected $_from   = null;
 
@@ -64,11 +63,8 @@ class Join
 
     /**
      * Constructor.
-     *
-     * @param   \Hoa\Database\Query\Select  $parent    Parent query.
-     * @param   array                       $from      FROM entry (“friends”).
      */
-    public function __construct(Select $parent, array &$from)
+    public function __construct(Select $parent, ?array &$from)
     {
         $this->_parent = $parent;
         $this->_from   = &$from;
@@ -79,11 +75,8 @@ public function __construct(Select $parent, array &$from)
 
     /**
      * Declare the JOIN constraint ON.
-     *
-     * @param   string  $expression    Expression.
-     * @return  \Hoa\Database\Query\Select
      */
-    public function on($expression)
+    public function on(string $expression): Select
     {
         $this->_from[key($this->_from)] =
             current($this->_from) .
@@ -94,17 +87,13 @@ public function on($expression)
 
     /**
      * Declare the JOIN constraint USING.
-     *
-     * @param   string  $expression    Expression.
-     * @param   ...     ...
-     * @return  \Hoa\Database\Query\Select
      */
-    public function using($expression)
+    public function using(string ...$expressions) : Select
     {
         $this->_from[key($this->_from)] =
             current($this->_from) .
             ' USING (' .
-            implode(', ', func_get_args()) . ')';
+            implode(', ', $expressions) . ')';
 
         return $this->_parent;
     }
diff --git a/Query/Query.php b/Source/Query/Query.php
similarity index 72%
rename from Query/Query.php
rename to Source/Query/Query.php
index e66e065..012f3ea 100644
--- a/Query/Query.php
+++ b/Source/Query/Query.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * Hoa
  *
@@ -42,9 +44,6 @@
  * Class \Hoa\Database\Query.
  *
  * Multiton of queries.
- *
- * @copyright  Copyright © 2007-2017 Hoa community
- * @license    New BSD License
  */
 class Query
 {
@@ -58,7 +57,7 @@ class Query
     /**
      * Current instance ID.
      *
-     * @var string
+     * @var ?string
      */
     protected $_id             = null;
 
@@ -66,11 +65,8 @@ class Query
 
     /**
      * Set current instance ID.
-     *
-     * @param   string  $id    ID.
-     * @return  \Hoa\Database\Query
      */
-    public function setId($id)
+    public function setId(string $id): self
     {
         $this->_id = $id;
 
@@ -79,63 +75,48 @@ public function setId($id)
 
     /**
      * Get current instance ID.
-     *
-     * @return  string
      */
-    public function getId()
+    public function getId(): ?string
     {
         return $this->_id;
     }
 
     /**
      * Start a START query.
-     *
-     * @param   string  $column    Column.
-     * @param   ...     ...
-     * @return  \Hoa\Database\Query\Select
      */
-    public function select($column = null)
+    public function select(string ...$columns): Select
     {
-        return $this->store(new Select(func_get_args()));
+        return $this->store(new Select($columns));
     }
 
     /**
      * Start an INSERT query.
-     *
-     * @return  \Hoa\Database\Query\Insert
      */
-    public function insert()
+    public function insert(): Insert
     {
         return $this->store(new Insert());
     }
 
     /**
      * Start an UPDATE query.
-     *
-     * @return  \Hoa\Database\Query\Update
      */
-    public function update()
+    public function update(): Update
     {
         return $this->store(new Update());
     }
 
     /**
      * Start a DELETE query.
-     *
-     * @return  \Hoa\Database\Query\Delete
      */
-    public function delete()
+    public function delete(): Delete
     {
         return $this->store(new Delete());
     }
 
     /**
      * Start a WHERE clause.
-     *
-     * @param   string  $expression    Expression.
-     * @return  \Hoa\Database\Query\Where
      */
-    public function where($expression)
+    public function where(string $expression): Where
     {
         $where = new Where();
 
@@ -144,9 +125,6 @@ public function where($expression)
 
     /**
      * Store the current instance if necessary.
-     *
-     * @param   \Hoa\Database\Query\Dml  $object    Object.
-     * @return  \Hoa\Database\Query\Dml
      */
     protected function store($object)
     {
@@ -163,11 +141,8 @@ protected function store($object)
 
     /**
      * Get a query (a clone of it).
-     *
-     * @param   string  $id    ID.
-     * @return  \Hoa\Database\Query\Dml
      */
-    public static function get($id)
+    public static function get(string $id): ?Dml
     {
         if (null === $out = static::getReference($id)) {
             return null;
@@ -178,11 +153,8 @@ public static function get($id)
 
     /**
      * Get a query (not a clone of it).
-     *
-     * @param   string  $id    ID.
-     * @return  \Hoa\Database\Query\Dml
      */
-    public static function getReference($id)
+    public static function getReference(string $id): ?Dml
     {
         if (false === array_key_exists($id, static::$_queries)) {
             return null;
@@ -195,4 +167,4 @@ public static function getReference($id)
 /**
  * Flex entity.
  */
-Consistency::flexEntity('Hoa\Database\Query\Query');
+Consistency::flexEntity(Query::class);
diff --git a/Query/Select.php b/Source/Query/Select.php
similarity index 77%
rename from Query/Select.php
rename to Source/Query/Select.php
index d928d77..13a974a 100644
--- a/Query/Select.php
+++ b/Source/Query/Select.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * Hoa
  *
@@ -40,9 +42,6 @@
  * Class \Hoa\Database\Query\Select.
  *
  * Build a SELECT query.
- *
- * @copyright  Copyright © 2007-2017 Hoa community
- * @license    New BSD License
  */
 class Select extends SelectCore implements Dml
 {
@@ -70,7 +69,7 @@ class Select extends SelectCore implements Dml
     /**
      * Offset expression.
      *
-     * @var string
+     * @var ?string
      */
     protected $_offset  = null;
 
@@ -78,51 +77,40 @@ class Select extends SelectCore implements Dml
 
     /**
      * Start a new SELECT query which is an union of the previous one.
-     *
-     * @return  \Hoa\Database\Query\Select
      */
-    public function union()
+    public function union(): self
     {
         return $this->compose('UNION');
     }
 
     /**
      * Start a new SELECT query which is an unionAll of the previous one.
-     *
-     * @return  \Hoa\Database\Query\Select
      */
-    public function unionAll()
+    public function unionAll(): self
     {
         return $this->compose('UNION ALL');
     }
 
     /**
      * Start a new SELECT query which is an intersection of the previous one.
-     *
-     * @return  \Hoa\Database\Query\Select
      */
-    public function intersect()
+    public function intersect(): self
     {
         return $this->compose('INTERSECT');
     }
 
     /**
      * Start a new SELECT query which is an exception of the previous one.
-     *
-     * @return  \Hoa\Database\Query\Select
      */
-    public function except()
+    public function except(): self
     {
         return $this->compose('EXCEPT');
     }
 
     /**
      * Compose SELECT queries.
-     *
-     * @param   string  $operator    Composition operator.
-     * @return  \Hoa\Database\Query\Select
      */
-    protected function compose($operator)
+    protected function compose(string $operator): self
     {
         $this->_select[] = parent::__toString() . ' ' . $operator;
         $this->reset();
@@ -132,14 +120,10 @@ protected function compose($operator)
 
     /**
      * Add ordering terms.
-     *
-     * @param   string  $term    Term.
-     * @param   ...     ...
-     * @return  \Hoa\Database\Query\Select
      */
-    public function orderBy($term)
+    public function orderBy(string ...$terms): self
     {
-        foreach (func_get_args() as $term) {
+        foreach ($terms as $term) {
             $this->_orderBy[] = $term;
         }
 
@@ -148,14 +132,10 @@ public function orderBy($term)
 
     /**
      * Add limit expressions.
-     *
-     * @param   string  $expression    Expression.
-     * @param   ...     ...
-     * @return  \Hoa\Database\Query\Select
      */
-    public function limit($expression)
+    public function limit(int ...$expressions): self
     {
-        foreach (func_get_args() as $expression) {
+        foreach ($expressions as $expression) {
             $this->_limit[] = $expression;
         }
 
@@ -164,11 +144,8 @@ public function limit($expression)
 
     /**
      * Add offset expression.
-     *
-     * @param   string  $expression    Expression.
-     * @return  \Hoa\Database\Query\Select
      */
-    public function offset($expression)
+    public function offset(string $expression): self
     {
         $this->_offset = $expression;
 
@@ -177,12 +154,10 @@ public function offset($expression)
 
     /**
      * Generate the query.
-     *
-     * @return  string
      */
-    public function __toString()
+    public function __toString(): string
     {
-        $out    = null;
+        $out    = '';
         $select = implode(' ', $this->_select);
 
         if (!empty($select)) {
diff --git a/Query/SelectCore.php b/Source/Query/SelectCore.php
similarity index 70%
rename from Query/SelectCore.php
rename to Source/Query/SelectCore.php
index e4d39ab..85887f1 100644
--- a/Query/SelectCore.php
+++ b/Source/Query/SelectCore.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * Hoa
  *
@@ -36,13 +38,12 @@
 
 namespace Hoa\Database\Query;
 
+use Hoa\Database\Exception;
+
 /**
  * Class \Hoa\Database\Query\SelectCore.
  *
  * Core of the SELECT query.
- *
- * @copyright  Copyright © 2007-2017 Hoa community
- * @license    New BSD License
  */
 abstract class SelectCore extends Where
 {
@@ -53,12 +54,12 @@ abstract class SelectCore extends Where
      *
      * @var array
      */
-    protected $_columns       = null;
+    protected $_columns       = [];
 
     /**
      * SELECT DISTINCT or SELECT ALL.
      *
-     * @var string
+     * @var ?string
      */
     protected $_distinctOrAll = null;
 
@@ -79,7 +80,7 @@ abstract class SelectCore extends Where
     /**
      * Having expression.
      *
-     * @var string
+     * @var ?string
      */
     protected $_having        = null;
 
@@ -87,8 +88,6 @@ abstract class SelectCore extends Where
 
     /**
      * Set columns.
-     *
-     * @param   array  $columns    Columns.
      */
     public function __construct(array $columns = [])
     {
@@ -99,10 +98,8 @@ public function __construct(array $columns = [])
 
     /**
      * Make a SELECT DISTINCT.
-     *
-     * @return  \Hoa\Database\Query\SelectCore
      */
-    public function distinct()
+    public function distinct(): self
     {
         $this->_distinctOrAll = 'DISTINCT';
 
@@ -111,10 +108,8 @@ public function distinct()
 
     /**
      * Make a SELECT ALL.
-     *
-     * @return  \Hoa\Database\Query\SelectCore
      */
-    public function all()
+    public function all(): self
     {
         $this->_distinctOrAll = 'ALL';
 
@@ -123,14 +118,10 @@ public function all()
 
     /**
      * Select a column.
-     *
-     * @param   string  $column    Column.
-     * @param   ...     ...
-     * @return  \Hoa\Database\Query\SelectCore
      */
-    public function select($column)
+    public function select(string ...$columns): self
     {
-        foreach (func_get_args() as $column) {
+        foreach ($columns as $column) {
             $this->_columns[] = $column;
         }
 
@@ -139,14 +130,10 @@ public function select($column)
 
     /**
      * Group by expression.
-     *
-     * @param   string  $expression    Expression.
-     * @param   ...     ...
-     * @return  \Hoa\Database\Query\SelectCore
      */
-    public function groupBy($expression)
+    public function groupBy(string ...$expressions): self
     {
-        foreach (func_get_args() as $expression) {
+        foreach ($expressions as $expression) {
             $this->_groupBy[] = $expression;
         }
 
@@ -155,11 +142,8 @@ public function groupBy($expression)
 
     /**
      * Having expression.
-     *
-     * @param   string  $expression    Expression.
-     * @return  \Hoa\Database\Query\SelectCore
      */
-    public function having($expression)
+    public function having(string $expression): self
     {
         $this->_having = $expression;
 
@@ -168,14 +152,10 @@ public function having($expression)
 
     /**
      * Set source (regular or a SELECT query).
-     *
-     * @param   mixed  $source    Source.
-     * @param   ...    ...
-     * @return  \Hoa\Database\Query\SelectCore
      */
-    public function from($source)
+    public function from(...$sources): self
     {
-        foreach (func_get_args() as $source) {
+        foreach ($sources as $source) {
             if ($source instanceof self) {
                 $source = '(' . $source . ')';
             }
@@ -188,11 +168,8 @@ public function from($source)
 
     /**
      * Alias the last declared source.
-     *
-     * @param   string  $alias    Alias.
-     * @return  \Hoa\Database\Query\SelectCore
      */
-    public function _as($alias)
+    public function _as(string $alias): self
     {
         if (empty($this->_from)) {
             return $this;
@@ -205,125 +182,91 @@ public function _as($alias)
 
     /**
      * Join a source (regular of a SELECT query).
-     *
-     * @param   mixed  $source    Source.
-     * @return  \Hoa\Database\Query\Join
      */
-    public function join($source)
+    public function join($source): Join
     {
         return $this->_join('JOIN', $source);
     }
 
     /**
      * Natural join a source (regular of a SELECT query).
-     *
-     * @param   mixed  $source    Source.
-     * @return  \Hoa\Database\Query\Join
      */
-    public function naturalJoin($source)
+    public function naturalJoin($source): Join
     {
         return $this->_join('NATURAL JOIN', $source);
     }
 
     /**
      * Left join a source (regular of a SELECT query).
-     *
-     * @param   mixed  $source    Source.
-     * @return  \Hoa\Database\Query\Join
      */
-    public function leftJoin($source)
+    public function leftJoin($source): Join
     {
         return $this->_join('LEFT JOIN', $source);
     }
 
     /**
      * Natural left join a source (regular of a SELECT query).
-     *
-     * @param   mixed  $source    Source.
-     * @return  \Hoa\Database\Query\Join
      */
-    public function naturalLeftJoin($source)
+    public function naturalLeftJoin($source): Join
     {
         return $this->_join('NATURAL LEFT JOIN', $source);
     }
 
     /**
      * Left outer join a source (regular of a SELECT query).
-     *
-     * @param   mixed  $source    Source.
-     * @return  \Hoa\Database\Query\Join
      */
-    public function leftOuterJoin($source)
+    public function leftOuterJoin($source): Join
     {
         return $this->_join('LEFT OUTER JOIN', $source);
     }
 
     /**
      * Natural left outer join a source (regular of a SELECT query).
-     *
-     * @param   mixed  $source    Source.
-     * @return  \Hoa\Database\Query\Join
      */
-    public function naturalLeftOuterJoin($source)
+    public function naturalLeftOuterJoin($source): Join
     {
         return $this->_join('NATURAL LEFT OUTER JOIN', $source);
     }
 
     /**
      * Inner join a source (regular of a SELECT query).
-     *
-     * @param   mixed  $source    Source.
-     * @return  \Hoa\Database\Query\Join
      */
-    public function innerJoin($source)
+    public function innerJoin($source): Join
     {
         return $this->_join('INNER JOIN', $source);
     }
 
     /**
      * Natural inner join a source (regular of a SELECT query).
-     *
-     * @param   mixed  $source    Source.
-     * @return  \Hoa\Database\Query\Join
      */
-    public function naturalInnerJoin($source)
+    public function naturalInnerJoin($source): Join
     {
         return $this->_join('NATURAL INNER JOIN', $source);
     }
 
     /**
      * Cross join a source (regular of a SELECT query).
-     *
-     * @param   mixed  $source    Source.
-     * @return  \Hoa\Database\Query\Join
      */
-    public function crossJoin($source)
+    public function crossJoin($source): Join
     {
         return $this->_join('CROSS JOIN', $source);
     }
 
     /**
      * Natural cross join a source (regular of a SELECT query).
-     *
-     * @param   mixed  $source    Source.
-     * @return  \Hoa\Database\Query\Join
      */
-    public function naturalCrossJoin($source)
+    public function naturalCrossJoin($source): Join
     {
         return $this->_join('NATURAL CROSS JOIN', $source);
     }
 
     /**
      * Make a join.
-     *
-     * @param   string  $type      Type.
-     * @param   mixed   $source    Source.
-     * @return  \Hoa\Database\Query\Join
      */
-    protected function _join($type, $source)
+    protected function _join(string $type, $source): Join
     {
         if (empty($this->_from)) {
-            return $this;
+            throw new Exception('Cannot join if there is no `FROM` set.', 0);
         }
 
         if ($source instanceof self) {
@@ -343,10 +286,8 @@ protected function _join($type, $source)
 
     /**
      * Reset some properties.
-     *
-     * @return  \Hoa\Database\Query\SelectCore
      */
-    public function reset()
+    public function reset(): parent
     {
         parent::reset();
         $this->_columns       = [];
@@ -360,10 +301,8 @@ public function reset()
 
     /**
      * Generate the query.
-     *
-     * @return  string
      */
-    public function __toString()
+    public function __toString(): string
     {
         $out = 'SELECT';
 
diff --git a/Query/Update.php b/Source/Query/Update.php
similarity index 76%
rename from Query/Update.php
rename to Source/Query/Update.php
index 35bc05f..b00fe96 100644
--- a/Query/Update.php
+++ b/Source/Query/Update.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * Hoa
  *
@@ -40,9 +42,6 @@
  * Class \Hoa\Database\Query\Update.
  *
  * Build an UPDATE query.
- *
- * @copyright  Copyright © 2007-2017 Hoa community
- * @license    New BSD License
  */
 class Update extends Where implements Dml
 {
@@ -51,14 +50,14 @@ class Update extends Where implements Dml
     /**
      * Table.
      *
-     * @var string
+     * @var ?string
      */
     protected $_table = null;
 
     /**
      * Alternative to UPDATE.
      *
-     * @var string
+     * @var ?string
      */
     protected $_or    = null;
 
@@ -73,61 +72,48 @@ class Update extends Where implements Dml
 
     /**
      * Update or rollback.
-     *
-     * @return  \Hoa\Database\Query\Update
      */
-    public function rollback()
+    public function rollback(): self
     {
         return $this->_or('ROLLBACK');
     }
 
     /**
      * Update or abort.
-     *
-     * @return  \Hoa\Database\Query\Update
      */
-    public function abort()
+    public function abort(): self
     {
         return $this->_or('ABORT');
     }
 
     /**
      * Update or replace.
-     *
-     * @return  \Hoa\Database\Query\Update
      */
-    public function replace()
+    public function replace(): self
     {
         return $this->_or('REPLACE');
     }
 
     /**
      * Update or fail.
-     *
-     * @return  \Hoa\Database\Query\Update
      */
-    public function fail()
+    public function fail(): self
     {
         return $this->_or('FAIL');
     }
 
     /**
      * Update or ignore.
-     *
-     * @return  \Hoa\Database\Query\Update
      */
-    public function ignore()
+    public function ignore(): self
     {
         return $this->_or('IGNORE');
     }
 
     /**
      * Declare an alternative to “INSERT”.
-     *
-     * @param   string  $or    Alternative.
-     * @return  \Hoa\Database\Query\Update
      */
-    protected function _or($or)
+    protected function _or(string $or): self
     {
         $this->_or = $or;
 
@@ -136,11 +122,8 @@ protected function _or($or)
 
     /**
      * Set the table.
-     *
-     * @param   string  $table    Table.
-     * @return  \Hoa\Database\Query\Update
      */
-    public function table($table)
+    public function table(string $table): self
     {
         $this->_table = $table;
 
@@ -149,12 +132,8 @@ public function table($table)
 
     /**
      * Set a pair.
-     *
-     * @param   string  $name     Name.
-     * @param   mixed   $value    Value.
-     * @return  \Hoa\Database\Query\Update
      */
-    public function set($name, $value)
+    public function set(string $name, $value): self
     {
         $this->_set[$name] = $value;
 
@@ -163,10 +142,8 @@ public function set($name, $value)
 
     /**
      * Generate the query.
-     *
-     * @return  string
      */
-    public function __toString()
+    public function __toString(): string
     {
         $out = 'UPDATE';
 
diff --git a/Query/Where.php b/Source/Query/Where.php
similarity index 79%
rename from Query/Where.php
rename to Source/Query/Where.php
index 61e8dd6..d4f2daf 100644
--- a/Query/Where.php
+++ b/Source/Query/Where.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * Hoa
  *
@@ -40,9 +42,6 @@
  * Class \Hoa\Database\Query\Where.
  *
  * Build a WHERE clause.
- *
- * @copyright  Copyright © 2007-2017 Hoa community
- * @license    New BSD License
  */
 class Where
 {
@@ -56,7 +55,7 @@ class Where
     /**
      * Current logic operator.
      *
-     * @var string
+     * @var ?string
      */
     protected $_logicOperator = null;
 
@@ -64,11 +63,8 @@ class Where
 
     /**
      * Add an expression (regular string or a WHERE clause).
-     *
-     * @param   mixed  $expression    Expression.
-     * @return  \Hoa\Database\Query\Where
      */
-    public function where($expression)
+    public function where($expression): self
     {
         $where = null;
 
@@ -77,7 +73,7 @@ public function where($expression)
         }
 
         if ($expression instanceof self) {
-            $expression = '(' . substr($expression, 7) . ')';
+            $expression = '(' . substr((string) $expression, 7) . ')';
         }
 
         $this->_where[]       = $where . $expression;
@@ -88,23 +84,16 @@ public function where($expression)
 
     /**
      * Redirect undefined calls to _calls.
-     *
-     * @param   string  $name      Name.
-     * @param   array   $values    Values.
-     * @return  \Hoa\Database\Query\Where
      */
-    public function __call($name, array $values)
+    public function __call(string $name, array $values): self
     {
         return call_user_func_array([$this, '_' . $name], $values);
     }
 
     /**
      * Set the current logic operator.
-     *
-     * @param   string  $name   Name.
-     * @return  \Hoa\Database\Query\Where
      */
-    public function __get($name)
+    public function __get(string $name): self
     {
         switch (strtolower($name)) {
             case 'and':
@@ -122,10 +111,8 @@ public function __get($name)
 
     /**
      * Reset.
-     *
-     * @return  \Hoa\Database\Query\Where
      */
-    public function reset()
+    public function reset(): self
     {
         $this->_where = [];
 
@@ -134,13 +121,11 @@ public function reset()
 
     /**
      * Generate the query.
-     *
-     * @return  string
      */
-    public function __toString()
+    public function __toString(): string
     {
         if (empty($this->_where)) {
-            return null;
+            return '';
         }
 
         return ' WHERE ' . implode(' ', $this->_where);
diff --git a/Test/Unit/Query/EncloseIdentifier.php b/Test/Unit/Query/EncloseIdentifier.php
index 30dd379..9730d1e 100644
--- a/Test/Unit/Query/EncloseIdentifier.php
+++ b/Test/Unit/Query/EncloseIdentifier.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * Hoa
  *
@@ -43,9 +45,6 @@
  * Class \Hoa\Database\Test\Unit\Query\EncloseIdentifier.
  *
  * Test suite of EncloseIdentifier feature.
- *
- * @copyright  Copyright © 2007-2017 Hoa community
- * @license    New BSD License
  */
 class EncloseIdentifier extends Test\Unit\Suite
 {
@@ -126,7 +125,7 @@ public function case_select()
                     ->groupBy('a')
                     ->having('"a" > 42') // manual enclose
                     ->orderBy('a')
-                    ->limit('2')
+                    ->limit(2)
                     ->offset('1')
             )
             ->then
@@ -154,7 +153,7 @@ public function case_select_expr()
                     ->groupBy('a')
                     ->having('"a" > 42') // manual enclose
                     ->orderBy('a')
-                    ->limit('2')
+                    ->limit(2)
                     ->offset('1')
             )
             ->then
@@ -182,7 +181,7 @@ public function case_select_alias()
                     ->groupBy('a')
                     ->having('"a" > 42') // manual enclose
                     ->orderBy('a')
-                    ->limit('2')
+                    ->limit(2)
                     ->offset('1')
             )
             ->then
diff --git a/Test/Unit/Query/Example.php b/Test/Unit/Query/Example.php
index 175bc79..36365fd 100644
--- a/Test/Unit/Query/Example.php
+++ b/Test/Unit/Query/Example.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * Hoa
  *
@@ -43,9 +45,6 @@
  * Class \Hoa\Database\Test\Unit\Query\Example.
  *
  * Test suite of some examples.
- *
- * @copyright  Copyright © 2007-2017 Hoa community
- * @license    New BSD License
  */
 class Example extends Test\Unit\Suite implements Test\Decorrelated
 {
@@ -91,7 +90,7 @@ public function case_bigger_one()
                                      ->select('c')
                                      ->from('bar')
                                      ->orderBy('c')
-                                     ->limit('2')
+                                     ->limit(2)
                                      ->offset('1')
             )
             ->then
diff --git a/composer.json b/composer.json
index a8b9ed7..787ad54 100644
--- a/composer.json
+++ b/composer.json
@@ -24,21 +24,22 @@
         "source": "https://central.hoa-project.net/Resource/Library/Database"
     },
     "require": {
-        "php"            : ">=5.5.0",
-        "hoa/consistency": "~1.0",
-        "hoa/event"      : "~1.0",
-        "hoa/exception"  : "~1.0",
-        "hoa/iterator"   : "~2.0",
-        "hoa/protocol"   : "~1.0",
-        "hoa/zformat"    : "~1.0",
+        "php"            : ">=7.1",
+        "hoa/consistency": "dev-master",
+        "hoa/event"      : "dev-master",
+        "hoa/exception"  : "dev-master",
+        "hoa/iterator"   : "dev-master",
+        "hoa/protocol"   : "dev-master",
+        "hoa/zformat"    : "dev-master",
         "ext-pdo"        : "*"
     },
     "require-dev": {
-        "hoa/test": "~2.0"
+        "hoa/test": "dev-master"
     },
     "autoload": {
         "psr-4": {
-            "Hoa\\Database\\": "."
+            "Hoa\\Database\\"      : "Source",
+            "Hoa\\Database\\Test\\": "Test"
         }
     },
     "extra": {