.post problem

.post problem

I use the function .post to get a DOM document provided by a php file. The problem is that the data received by the function and stored in a variable is all the code of the php file not the DOM document asked.
The strange thing is which in Chrome the script works well, but in Firefox doesn't work.

Here is the code of both files:

JQuery script:

$(document).ready(function(){
$.post('ejemplo1.php',processData);
     function processData(data) {
       var xml = $.xmlDOM( data );
var nom_host = $(xml).find('pass_usuario').text();
$('<div class="nom_host"></div>').html(nom_host).appendTo('#page-wrap');
   } // end processData

}); //Fin ready


PHP file:

<?php

//I need to load the xml file using php because I will use semaphores to limit access/modifies.

//Tratamiento del XML
$xmlDoc = new DOMDocument();
$xmlDoc->load('configuracion.xml');
echo $xmlDoc->saveXML();
?>

Thanks.