mcrypt
PHP Manual

mcrypt_enc_get_key_size

(PHP 4 >= 4.0.2, PHP 5)

mcrypt_enc_get_key_size — Returns the maximum supported keysize of the opened mode

Description

int mcrypt_enc_get_key_size ( resource $td )

This function returns the maximum supported key size of the algorithm specified by the encryption descriptor td in bytes.


mcrypt
PHP Manual