#keywords PHP,PHP4,HMAC,Hash

some.php
{{{#!php
<?php
if (!defined('PHP_VERSION_ID')) {
  $version = explode('.', PHP_VERSION);

  define('PHP_VERSION_ID', ($version[0] * 10000 + $version[1] * 100 + $version[2]));
}
if ($version[0] == 4)
  require_once("lib/hash_hmac.php");

$hmac = hash_hmac('sha256', $url, SECRET_KEY);
?>
}}}

lib\hash_hmac.php
{{{#!php
<?php

require_once dirname(__FILE__) . '/hash.php';

/**
 * Replace hash_hmac()
 *
 * @category    PHP
 * @package     PHP_Compat
 * @license     LGPL - http://www.gnu.org/licenses/lgpl.html
 * @copyright   2004-2007 Aidan Lister <aidan@php.net>, Arpad Ray <arpad@php.net>
 * @link        http://php.net/function.hash_hmac
 * @author      revulo <revulon@gmail.com>
 * @since       PHP 5.1.2
 * @require     PHP 4.0.1 (str_pad)
 */
function php_compat_hash_hmac($algo, $data, $key, $raw_output = false)
{
    // Block size (byte) for MD5, SHA-1 and SHA-256.
    $blocksize = 64;

    $ipad = str_repeat("\x36", $blocksize);
    $opad = str_repeat("\x5c", $blocksize);

    if (strlen($key) > $blocksize) {
        $key = hash($algo, $key, true);
    } else {
        $key = str_pad($key, $blocksize, "\x00");
    }

    $ipad ^= $key;
    $opad ^= $key;

    return hash($algo, $opad . hash($algo, $ipad . $data, true), $raw_output);
}


// Define
if (!function_exists('hash_hmac')) {
    function hash_hmac($algo, $data, $key, $raw_output = false)
    {
        return php_compat_hash_hmac($algo, $data, $key, $raw_output);
    }
}
}}}

lib\hash.php
{{{#!php
<?php

/**
 * Replace hash()
 *
 * @category    PHP
 * @package     PHP_Compat
 * @license     LGPL - http://www.gnu.org/licenses/lgpl.html
 * @copyright   2004-2007 Aidan Lister <aidan@php.net>, Arpad Ray <arpad@php.net>
 * @link        http://php.net/function.hash
 * @author      revulo <revulon@gmail.com>
 * @since       PHP 5.1.2
 * @require     PHP 4.0.0 (user_error)
 */
function php_compat_hash($algo, $data, $raw_output = false)
{
    $algo = strtolower($algo);
    switch ($algo) {
        case 'md5':
            $hash = md5($data);
            break;

        case 'sha1':
            if (!function_exists('sha1')) {
                require dirname(__FILE__) . '/sha1.php';
            }
            $hash = sha1($data);
            break;

        case 'sha256':
            //if (!function_exists('php_compat_sha256')) {
            //    require dirname(__FILE__) . '/_sha256.php';
            //}
            //$hash = php_compat_sha256($data);

            require_once dirname(__FILE__) . '/sha256.php';
            $hash = SHA256::hash($data);
            break;

        default:
            user_error('hash(): Unknown hashing algorithm: ' . $algo, E_USER_WARNING);
            return false;
    }

    if ($raw_output) {
        return pack('H*', $hash);
    } else {
        return $hash;
    }
}


// Define
if (!function_exists('hash')) {
    function hash($algo, $data, $raw_output = false)
    {
        return php_compat_hash($algo, $data, $raw_output);
    }
}
}}}

attachment:sha256.php