PHP mcrypt_encrypt Function: Parameters, Usage, and Return Value

string mcrypt_encrypt ( string $cipher , string $key , string $data , string $mode [, string $iv] )

The mcrypt_encrypt function encrypts data using a given cipher, key, mode, and optional initialization vector (IV), returning the ciphertext as a string or FALSE on failure.

Parameters

cipher : One of the MCRYPT_ciphername constants or a string naming the algorithm.

key : The encryption key; if its length is unsupported, a warning is issued and the function returns FALSE .

data : The plaintext to encrypt; if its length is not a multiple of the block size, it is padded with "\0".

mode : One of the MCRYPT_MODE_modename constants or the strings "ecb", "cbc", "cfb", "ofb", "nofb", "stream".

iv (optional): Initialization vector used in CBC, CFB, OFB modes and some stream algorithms; missing or incorrect size triggers a warning and returns FALSE .

Return value

Returns the ciphertext as a string; on failure it returns FALSE .