(PHP 4 >= 4.0.2, PHP 5)
mcrypt_module_get_supported_key_sizes — Returns an array with the supported keysizes of the opened algorithm
$algorithm
   [, string $lib_dir
  ] )Returns an array with the key sizes supported by the specified algorithm. If it returns an empty array then all key sizes between 1 and mcrypt_module_get_algo_key_size() are supported by the algorithm.
algorithmThe algorithm to be used.
lib_dir
       The optional lib_dir parameter can contain the
       location where the algorithm module is on the system.
      
Returns an array with the key sizes supported by the specified algorithm. If it returns an empty array then all key sizes between 1 and mcrypt_module_get_algo_key_size() are supported by the algorithm.