Mhash
PHP Manual

Examples

Example #1 Computes the MD5 digest and hmac and print it out as hex

<?php
$input = "what do ya want for nothing?";
$hash = mhash(MHASH_MD5, $input);
echo "The hash is " . bin2hex($hash) . "<br />\n";
$hash = mhash(MHASH_MD5, $input, "Jefe");
echo "The hmac is " . bin2hex($hash) . "<br />\n";
?>

The above example will output:

The hash is d03cb659cbf9192dcd066272249f8412 
The hmac is 750c783e6ab0b503eaa86e310a5db738