... string mcrypt_decrypt ( string cipher, string key, string data, string mode [, string iv]) . ... Cipher is one of the MCRYPT_ciphername constants of the name of the algorithm as string. ... Data is the data that will be decrypted with the given cipher and mode. ... Mode is one of the MCRYPT_MODE_modename constants of one of "ecb", "cbc", "cfb", "ofb", "nofb" or "stream". The IV parameter is used for the initialisation in CBC, CFB, OFB modes, and in some algorithms in STREAM mode. ...