Creating a Zend Server Web API request signature using PHP

zs_request_sign.php

<?php

/**
 * Calculate Zend Server Web API request signature
 * 
 * @param  string  $host      Exact value of the 'Host:' HTTP header
 * @param  string  $path      Request URI
 * @param  integer $timestamp Timestamp used for the 'Date:' HTTP header
 * @param  string  $userAgent Exact value of the 'User-Agent:' HTTP header
 * @param  string  $apiKey    Zend Server API key
 * @return string             Calculated request signature
 */
function generateRequestSignature($host, $path, $timestamp, $userAgent, $apiKey)
{
    $data = $host . ":" . 
            $path . ":" . 
            $userAgent . ":" . 
            gmdate('D, d M y H:i:s ', $timestamp) . 'GMT';
    
    return hash_hmac('sha256', $data, $apiKey);
}