php man page for mcrypt_generic

MCRYPT_GENERIC(3)							 1							 MCRYPT_GENERIC(3)

mcrypt_generic - This function encrypts data

SYNOPSIS
       string mcrypt_generic (resource	$td, string  $data)

DESCRIPTION
	This function encrypts data. The data is padded with " " to make sure the length of the data is n * blocksize. This function returns the
       encrypted data. Note that the length of the returned string can in fact be longer than the input, due to the padding of the data.

	If you want to store the encrypted data in a database make sure to store the entire string as returned by mcrypt_generic,  or  the  string
       will not entirely decrypt properly. If your original string is 10 characters long and the block size is 8 (use mcrypt_enc_get_block_size(3)
       to determine the blocksize), you would need at least 16 characters in your database field. Note the string returned by  mdecrypt_generic(3)
       will be 16 characters as well...use rtrim($str, "") to remove the padding.

	If you are for example storing the data in a MySQL database remember that varchar fields automatically have trailing spaces removed during
       insertion. As encrypted data can end in a space (ASCII 32), the data will be damaged by this removal. Store data in a tinyblob/tinytext (or
       larger) field instead.

PARAMETERS
	      o $td
		-  The encryption descriptor.  The encryption handle should always be initialized with mcrypt_generic_init(3) with a key and an IV
		before	calling  this  function.  Where  the  encryption  is  done,  you  should  free	 the   encryption   buffers   by   calling
		mcrypt_generic_deinit(3). See mcrypt_module_open(3) for an example.

	      o $data
		- The data to encrypt.

RETURN VALUES
	Returns the encrypted data.

SEE ALSO
       mdecrypt_generic(3), mcrypt_generic_init(3), mcrypt_generic_deinit(3).

PHP Documentation Group 													 MCRYPT_GENERIC(3)