使用base64编码的字符串将XML从Javascript发送到PHP

I have to send an XML via Javascript to PHP and am doing this via jQuery like this:

$.ajax({
           url             :   'http://myurl',
           type            :   'POST',
           data            :   { documentXML : escape(xml) },
           dataType        :   'text',
           success         :   function( data ) {
              // Do something
           },
           error           :   function() {
              alert('Failed to send ajax request!');
           }
        })

I'm decoding the xml in PHP like this:

if(isset($_REQUEST['documentXML'])) {
    $receivedXML = urldecode($_REQUEST['documentXML']);
} else {
   die('<?xml version="1.0"?><error>No documentXML given.</error>');
}

However, inside the XML there are other XMLs embedded; this is done by base64 encoding the embedded XMLs. The base64 turns invalid during this process.

Given that changing the XML structure or the encoding is not an option:

• what can I do?
• is the way I'm doing this the right approach?

Thanks.