(PHP 4 >= 4.0.2)mcrypt_get_iv_size -- Returns the size of the IV belonging to a specific cipher/mode combination
The first prototype is when linked against libmcrypt 2.2.x, the second when linked against libmcrypt 2.4.x.
mcrypt_get_iv_size() returns the size of the Initialisation Vector (IV) in bytes. On error the function returns FALSE. If the IV is ignored in the specified cipher/mode combination zero is returned.
Cipher is one of the MCRYPT_ciphername constants of the name of the algorithm as string.
Mode is one of the MCRYPT_MODE_modename constants of one of "ecb", "cbc", "cfb", "ofb", "nofb" or "stream".
Td is the algorithm specified.