mcrypt_module_get_algo_key_size(3) php man page | unix.com

MCRYPT_MODULE_GET_ALGO_KEY_SIZE(3)					 1					MCRYPT_MODULE_GET_ALGO_KEY_SIZE(3)

mcrypt_module_get_algo_key_size - Returns the maximum supported keysize of the opened mode

SYNOPSIS
       int mcrypt_module_get_algo_key_size (string  $algorithm, [string  $lib_dir])

DESCRIPTION
	Gets the maximum supported keysize of the opened mode.

PARAMETERS
	      o $algorithm
		- The algorithm name.

	      o $lib_dir
		- This optional parameter can contain the location where the mode module is on the system.

RETURN VALUES
	This function returns the maximum supported key size of the algorithm specified in bytes.

PHP Documentation Group 											MCRYPT_MODULE_GET_ALGO_KEY_SIZE(3)