diff --git a/phpstan.neon.dist b/phpstan.neon.dist
index dfd417be..c1799961 100644
--- a/phpstan.neon.dist
+++ b/phpstan.neon.dist
@@ -1,9 +1,9 @@
 parameters:
   paths:
     - src
-  level: 0
+  level: 5
   ignoreErrors:
     - "#Parameter#"
     - "#Call to static method error\\(\\)\\ on an unknown class Log.#"
   excludePaths:
-    - "src/Providers/PayPalServiceProvider.php" 
\ No newline at end of file
+    - "src/Providers/PayPalServiceProvider.php"
diff --git a/src/PayPalFacadeAccessor.php b/src/PayPalFacadeAccessor.php
index dee1f220..3c5307c3 100644
--- a/src/PayPalFacadeAccessor.php
+++ b/src/PayPalFacadeAccessor.php
@@ -10,7 +10,7 @@ class PayPalFacadeAccessor
     /**
      * PayPal API provider object.
      *
-     * @var
+     * @var \Srmklive\PayPal\Services\PayPal
      */
     public static $provider;
 
diff --git a/src/Services/Str.php b/src/Services/Str.php
index 0fb4576f..15ac758e 100644
--- a/src/Services/Str.php
+++ b/src/Services/Str.php
@@ -20,14 +20,10 @@ public static function isJson($value): bool
         }
 
         if (function_exists('json_validate')) {
-            return json_validate($value, 512);
+            return json_validate($value);
         }
 
-        try {
-            Utils::jsonDecode($value, true, 512, 4194304);
-        } catch (\JsonException $jsonException) {
-            return false;
-        }
+        Utils::jsonDecode($value, true, 512, JSON_THROW_ON_ERROR);
 
         return true;
     }
diff --git a/src/Services/VerifyDocuments.php b/src/Services/VerifyDocuments.php
index 624687f9..ad815b54 100644
--- a/src/Services/VerifyDocuments.php
+++ b/src/Services/VerifyDocuments.php
@@ -17,12 +17,12 @@ class VerifyDocuments
     ];
 
     /**
-     * @var string
+     * @var int
      */
     protected static $dispute_evidence_file_size = 10;
 
     /**
-     * @var string
+     * @var int
      */
     protected static $dispute_evidences_size = 50;
 
diff --git a/src/Traits/PayPalAPI.php b/src/Traits/PayPalAPI.php
index 8bde8e61..b065dbe5 100644
--- a/src/Traits/PayPalAPI.php
+++ b/src/Traits/PayPalAPI.php
@@ -107,7 +107,7 @@ public function setPageSize(int $size): \Srmklive\PayPal\Services\PayPal
     /**
      * Set the current page for list resources API calls.
      *
-     * @param int $size
+     * @param int $page
      *
      * @return \Srmklive\PayPal\Services\PayPal
      */
diff --git a/src/Traits/PayPalAPI/DisputesActions.php b/src/Traits/PayPalAPI/DisputesActions.php
index 10613667..e7eac273 100644
--- a/src/Traits/PayPalAPI/DisputesActions.php
+++ b/src/Traits/PayPalAPI/DisputesActions.php
@@ -38,7 +38,7 @@ public function acknowledgeItemReturned(string $dispute_id, string $dispute_note
      * Providence evidence in support of a dispute.
      *
      * @param string $dispute_id
-     * @param array  $file_path
+     * @param array  $files
      *
      * @throws \Throwable
      *
diff --git a/src/Traits/PayPalAPI/InvoiceSearch/Filters.php b/src/Traits/PayPalAPI/InvoiceSearch/Filters.php
index 6160e980..e1a1e897 100644
--- a/src/Traits/PayPalAPI/InvoiceSearch/Filters.php
+++ b/src/Traits/PayPalAPI/InvoiceSearch/Filters.php
@@ -149,7 +149,15 @@ public function addInvoiceFilterByReferenceorMemo(string $reference, bool $memo
      */
     public function addInvoiceFilterByCurrencyCode(string $currency_code = ''): \Srmklive\PayPal\Services\PayPal
     {
-        $currency = !isset($currency_code) ? $this->getCurrency() : $currency_code;
+        if (!empty($currency_code)) {
+            $currency = $currency_code;
+        } else {
+            try {
+                $currency = $this->getCurrency();
+            } catch (\Throwable $e) {
+                $currency = 'USD';
+            }
+        }
 
         $this->invoice_search_filters['currency_code'] = $currency;
 
@@ -171,7 +179,15 @@ public function addInvoiceFilterByAmountRange(float $start_amount, float $end_am
             throw new \Exception('Starting amount should always be less than end amount!');
         }
 
-        $currency = !isset($amount_currency) ? $this->getCurrency() : $amount_currency;
+        if (!empty($amount_currency)) {
+            $currency = $amount_currency;
+        } else {
+            try {
+                $currency = $this->getCurrency();
+            } catch (\Throwable $e) {
+                $currency = 'USD';
+            }
+        }
 
         $this->invoice_search_filters['total_amount_range'] = [
             'lower_amount' => [
diff --git a/src/Traits/PayPalAPI/Subscriptions.php b/src/Traits/PayPalAPI/Subscriptions.php
index a43fb374..15e309b3 100644
--- a/src/Traits/PayPalAPI/Subscriptions.php
+++ b/src/Traits/PayPalAPI/Subscriptions.php
@@ -219,8 +219,8 @@ public function listSubscriptionTransactions(string $subscription_id, $start_dat
             $end_date = Carbon::parse($end_date);
         }
 
-        $start_date = $start_date->toIso8601ZuluString();
-        $end_date = $end_date->toIso8601ZuluString();
+        $start_date = $start_date->format('Y-m-d\TH:i:s\Z');
+        $end_date = $end_date->format('Y-m-d\TH:i:s\Z');
 
         $this->apiEndPoint = "v1/billing/subscriptions/{$subscription_id}/transactions?start_time={$start_date}&end_time={$end_date}";
 
diff --git a/src/Traits/PayPalAPI/Subscriptions/Helpers.php b/src/Traits/PayPalAPI/Subscriptions/Helpers.php
index 3bc60833..d94dec86 100644
--- a/src/Traits/PayPalAPI/Subscriptions/Helpers.php
+++ b/src/Traits/PayPalAPI/Subscriptions/Helpers.php
@@ -19,19 +19,19 @@ trait Helpers
     protected $payment_failure_threshold = 3;
 
     /**
-     * @var array
+     * @var array|null
      */
-    protected $product;
+    protected ?array $product = null;
 
     /**
-     * @var array
+     * @var array|null
      */
-    protected $billing_plan;
+    protected ?array $billing_plan = null;
 
     /**
-     * @var array
+     * @var array|null
      */
-    protected $shipping_address;
+    protected ?array $shipping_address = null;
 
     /**
      * @var array
@@ -44,14 +44,19 @@ trait Helpers
     protected $has_setup_fee = false;
 
     /**
-     * @var array
+     * @var array|null
+     */
+    protected ?array $taxes = null;
+
+    /**
+     * @var string|null
      */
-    protected $taxes;
+    protected ?string $custom_id = null;
 
     /**
-     * @var string
+     * @var array
      */
-    protected $custom_id;
+    protected ?array $experience_context = [];
 
     /**
      * Setup a subscription.
@@ -121,7 +126,7 @@ public function setupSubscription(string $customer_name, string $customer_email,
      *
      * @param string    $interval_type
      * @param int       $interval_count
-     * @param float|int $price
+     * @param float     $price
      * @param int       $total_cycles
      *
      * @return \Srmklive\PayPal\Services\PayPal
@@ -138,7 +143,7 @@ public function addPlanTrialPricing(string $interval_type, int $interval_count,
      *
      * @param string    $name
      * @param string    $description
-     * @param float|int $price
+     * @param float     $price
      * @param int       $total_cycles
      *
      * @throws Throwable
@@ -164,7 +169,7 @@ public function addDailyPlan(string $name, string $description, float $price, in
      *
      * @param string    $name
      * @param string    $description
-     * @param float|int $price
+     * @param float     $price
      * @param int       $total_cycles
      *
      * @throws Throwable
@@ -190,7 +195,7 @@ public function addWeeklyPlan(string $name, string $description, float $price, i
      *
      * @param string    $name
      * @param string    $description
-     * @param float|int $price
+     * @param float     $price
      * @param int       $total_cycles
      *
      * @throws Throwable
@@ -216,7 +221,7 @@ public function addMonthlyPlan(string $name, string $description, float $price,
      *
      * @param string    $name
      * @param string    $description
-     * @param float|int $price
+     * @param float     $price
      * @param int       $total_cycles
      *
      * @throws Throwable
@@ -242,7 +247,7 @@ public function addAnnualPlan(string $name, string $description, float $price, i
      *
      * @param string    $name
      * @param string    $description
-     * @param float|int $price
+     * @param float     $price
      * @param string    $interval_unit
      * @param int       $interval_count
      * @param int       $total_cycles
@@ -327,14 +332,12 @@ public function addProduct(string $name, string $description, string $type, stri
             return $this;
         }
 
-        $request_id = Str::random();
-
         $product = $this->createProduct([
             'name'        => $name,
             'description' => $description,
             'type'        => $type,
             'category'    => $category,
-        ], $request_id);
+        ]);
 
         if ($error = data_get($product, 'error', false)) {
             throw new \RuntimeException(data_get($error, 'details.0.description', 'Failed to add product'));
@@ -389,8 +392,6 @@ public function addBillingPlanById(string $plan_id): \Srmklive\PayPal\Services\P
      */
     protected function addBillingPlan(string $name, string $description, array $billing_cycles): void
     {
-        $request_id = Str::random();
-
         $plan_params = [
             'product_id'          => $this->product['id'],
             'name'                => $name,
@@ -404,7 +405,7 @@ protected function addBillingPlan(string $name, string $description, array $bill
             ],
         ];
 
-        $billingPlan = $this->createPlan($plan_params, $request_id);
+        $billingPlan = $this->createPlan($plan_params);
         if ($error = data_get($billingPlan, 'error', false)) {
             throw new \RuntimeException(data_get($error, 'details.0.description', 'Failed to add billing plan'));
         }
diff --git a/src/Traits/PayPalAPI/Trackers.php b/src/Traits/PayPalAPI/Trackers.php
index 036b1d6c..4789b9f0 100644
--- a/src/Traits/PayPalAPI/Trackers.php
+++ b/src/Traits/PayPalAPI/Trackers.php
@@ -60,9 +60,9 @@ public function addTracking(array $data)
      *
      * @see https://developer.paypal.com/docs/api/tracking/v1/#trackers-batch_get
      */
-    public function listTrackingDetails(string $transaction_id, string $tracking_number = null)
+    public function listTrackingDetails(string $transaction_id, ?string $tracking_number = null)
     {
-        $this->apiEndPoint = "v1/shipping/trackers?transaction_id={$transaction_id}".!empty($tracking_number) ? "&tracking_number={$tracking_number}" : '';
+        $this->apiEndPoint = "v1/shipping/trackers?transaction_id={$transaction_id}".(!empty($tracking_number) ? "&tracking_number={$tracking_number}" : '');
 
         $this->verb = 'get';
 
diff --git a/src/Traits/PayPalExperienceContext.php b/src/Traits/PayPalExperienceContext.php
index d1db77a2..a0dbe634 100644
--- a/src/Traits/PayPalExperienceContext.php
+++ b/src/Traits/PayPalExperienceContext.php
@@ -7,7 +7,7 @@ trait PayPalExperienceContext
     /**
      * @var array
      */
-    protected $experience_context = [];
+    protected ?array $experience_context = [];
 
     /**
      * Set Brand Name when setting experience context for payment.
diff --git a/src/Traits/PayPalHttpClient.php b/src/Traits/PayPalHttpClient.php
index 7723b66c..ab4b6cd0 100644
--- a/src/Traits/PayPalHttpClient.php
+++ b/src/Traits/PayPalHttpClient.php
@@ -120,7 +120,7 @@ protected function defineCurlConstant(string $key, string $value)
      *
      * @return void
      */
-    public function setClient(HttpClient $client = null)
+    public function setClient(?HttpClient $client = null)
     {
         if ($client instanceof HttpClient) {
             $this->client = $client;
diff --git a/src/Traits/PayPalRequest.php b/src/Traits/PayPalRequest.php
index 362103cf..011b2a2c 100644
--- a/src/Traits/PayPalRequest.php
+++ b/src/Traits/PayPalRequest.php
@@ -55,7 +55,7 @@ trait PayPalRequest
     /**
      * Set the current page for list resources API calls.
      *
-     * @var bool
+     * @var int
      */
     protected $current_page = 1;
 
diff --git a/src/Traits/PayPalVerifyIPN.php b/src/Traits/PayPalVerifyIPN.php
index 63478683..37bb6887 100644
--- a/src/Traits/PayPalVerifyIPN.php
+++ b/src/Traits/PayPalVerifyIPN.php
@@ -2,6 +2,8 @@
 
 namespace Srmklive\PayPal\Traits;
 
+use Illuminate\Http\Request;
+
 trait PayPalVerifyIPN
 {
     protected $webhook_id;
@@ -16,12 +18,16 @@ public function setWebHookID(string $webhook_id): \Srmklive\PayPal\Services\PayP
     /**
      * Verify incoming IPN through a web hook id.
      *
+     * @param \Illuminate\Http\Request $request Laravel HTTP request object
      * @throws \Throwable
      *
      * @return array|\Psr\Http\Message\StreamInterface|string
+     *
+     * @phpstan-ignore-next-line
      */
-    public function verifyIPN(\Illuminate\Http\Request $request)
+    public function verifyIPN(Request $request)
     {
+        /** @phpstan-ignore-next-line */
         $headers = array_change_key_case($request->headers->all(), CASE_UPPER);
 
         if (!isset($headers['PAYPAL-AUTH-ALGO'][0]) ||
@@ -36,6 +42,7 @@ public function verifyIPN(\Illuminate\Http\Request $request)
             return ['error' => 'Invalid headers or webhook id provided'];
         }
 
+        /** @phpstan-ignore-next-line */
         $params = json_decode($request->getContent());
 
         $payload = [
diff --git a/tests/MockClientClasses.php b/tests/MockClientClasses.php
index 109fe3fe..0a4d784d 100644
--- a/tests/MockClientClasses.php
+++ b/tests/MockClientClasses.php
@@ -117,14 +117,7 @@ private function getApiCredentials(): array
 
     protected function setMethodsFunction(): bool
     {
-        $useOnlyMethods = false;
-
-        foreach (['8.1', '8.2', '8.3'] as $php_version) {
-            if (strpos(phpversion(), $php_version) !== false) {
-                $useOnlyMethods = true;
-            }
-        }
-
-        return $useOnlyMethods;
+        // Always use onlyMethods as setMethods is deprecated in PHPUnit 8 and removed in PHPUnit 10
+        return true;
     }
 }