php man page for hash_init

HASH_INIT(3)								 1							      HASH_INIT(3)

hash_init - Initialize an incremental hashing context

SYNOPSIS
       resource hash_init NULL (string	$algo, [int  $options], [string  $key])

DESCRIPTION
PARAMETERS
	      o $algo
		-  Name  of  selected  hashing	algorithm  (i.e.  "md5",  "sha256",  "haval160,4",  etc..). For a list of supported algorithms see
		hash_algos(3).

	      o $options
		- Optional settings for hash generation, currently supports only one option: HASH_HMAC. When specified, the $key  must	be  speci-
		fied.

	      o $key
		-  When  HASH_HMAC is specified for $options, a shared secret key to be used with the HMAC hashing method must be supplied in this
		parameter.

RETURN VALUES
	Returns a Hashing Context resource for use with hash_update(3), hash_update_stream(3), hash_update_file(3), and hash_final(3).

EXAMPLES
       Example #1

	      Incremental hashing example

	      <?php
	      $ctx = hash_init('md5');
	      hash_update($ctx, 'The quick brown fox ');
	      hash_update($ctx, 'jumped over the lazy dog.');
	      echo hash_final($ctx);
	      ?>

	      The above example will output:

	      5c6ffbdd40d9556b73a21e63c3e0e904

SEE ALSO
       hash(3), hash_algos(3), hash_file(3), hash_hmac(3), hash_hmac_file(3).

PHP Documentation Group 													      HASH_INIT(3)