(PHP 5 >= PHP 5.3.3)
openssl_cipher_iv_length — Gets the cipher iv length
Gets the cipher iv length.
The method.
Returns the cipher length on success, or FALSE on failure.
Emits an E_WARNING level error when the cipher algorithm is unknown.
Example #1 openssl_cipher_iv_length() example
<?php
$method = 'AES-128-CBC';
$ivlen = openssl_cipher_iv_length($method);
echo $ivlen;
?>
以上例程的输出类似于：
16