mcrypt_get_iv_size Returns the size of the IV belonging to a specific cipher/mode combination intmcrypt_get_iv_size stringcipher stringmode intmcrypt_get_iv_size resourcetd 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.