The return value is a length in bytes. (Not bits, or anything else.)
(PHP 5 >= PHP 5.3.3, PHP 7)
openssl_cipher_iv_length — Gets the cipher iv length
$method
)Gets the cipher initialization vector (iv) length.
methodThe cipher method, see openssl_get_cipher_methods() for a list of potential values.
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
The return value is a length in bytes. (Not bits, or anything else.)