To put a domain into a script
<p>I have a index.php which will be loaded on many sites</p>

<pre><code>&lt;?php
$id=$_GET[id];
header("HTTP/1.1 301 Moved Permanently");
header("Location: http://site1.com/?user_id=86&amp;res=".base64_encode("site2.ru")."&amp;dn=50&amp;delay=1&amp;de=".base64_encode("://SITE_DOMAIN/folder/?id=".$id));
exit;
?&gt;
</code></pre>

<p>How can this code be changed, if i need to fill the place "SITE_DOMAIN" with domain name, on which index.php is loaded?</p>
