api-example.php

<?php 
// Encode a string to URL-safe base64 
function encodeBase64UrlSafe($value) 
{ 
 return str_replace(array('+', '/'), array('-', '_'), 
 base64_encode($value)); 
}

// Decode a string from URL-safe base64 
function decodeBase64UrlSafe($value) 
{ 
 return base64_decode(str_replace(array('-', '_'), array('+', '/'), 
 $value)); 
}

// Sign a URL with a given crypto key 
// Note that this URL must be properly URL-encoded 
function signUrl($myUrlToSign, $privateKey) 
{ // Decode the private key into its binary format 
 $decodedKey = decodeBase64UrlSafe($privateKey); 
 // Create a signature using the private key and the URL-encoded 
 // string using HMAC SHA1. This signature will be binary. 
 $signature = hash_hmac("MD5",$myUrlToSign, $decodedKey, true); 
 $encodedSignature = encodeBase64UrlSafe($signature); 
 return $encodedSignature; 
}

$key = 'Encoding-Key'; 
$url = 'http://fake-domain.com/GetChapterEventList/?clientId=12345&chapterId=55';

$signature = signUrl($url, $key); 
$opts = array('http'=>array('header'=>"Authorization: " . $signature));

$context = stream_context_create($opts); 
$file = file_get_contents($url, false, $context); 
echo $file

?>