<?php

function hmac ($key, $data)

{

    // RFC 2104 HMAC implementation for php.

    // Creates an md5 HMAC.

    // Eliminates the need to install mhash to compute a HMAC

    // Hacked by Lance Rushing



    $b = 64; // byte length for md5

    if (strlen($key) > $b) {

        $key = pack("H*",md5($key));

    }

    $key  = str_pad($key, $b, chr(0x00));

    $ipad = str_pad('', $b, chr(0x36));

    $opad = str_pad('', $b, chr(0x5c));

    $k_ipad = $key ^ $ipad ;

    $k_opad = $key ^ $opad;



    return md5($k_opad  . pack("H*",md5($k_ipad . $data)));

}

?>