$iv should not be const/static

[gajosadrian]

According to the documentation, $iv (A non-null initialization vector) in openssl_encrypt as well in openssl_decrypt should be random in every environment. However, currently, it is static for the PHP package. For AES-256-CTR it should be 16 bytes.

php-openssl-cryptor/src/Cryptor.php

Line 61 in f62397b

$this->iv_num_bytes = openssl_cipher_iv_length($cipher_algo);