Pull parsing XML in PHP

$reader = new XMLReader();

If you find that $HTTP_RAW_POST_DATA is empty, add the following line to your php.ini file:
always_populate_raw_post_data = On

$request = $HTTP_RAW_POST_DATA;
$reader->XML($request);
while ($reader->read()) {
// processing code goes here...
}

$reader->close();

Source : http://www.ibm.com/developerworks/library/x-pullparsingphp.html