javascript - error reading the response :Invalid XML error -

i m checking if username exists in database using ajax php& mysql. browser throwing following error in popup:

error reading response: invalid xml

my hanleserverresponse() function:

function handleserverresponse() {     // retrieve server's response packaged xml dom object     var xmlresponse = xmlhttp.responsexml;      // catching potential errors ie , opera     if (!xmlresponse || !xmlresponse.documentelement)         throw("invalid xml structure:\n" + xmlhttp.responsetext);      // catching potential errors firefox     var rootnodename = xmlresponse.documentelement.nodename;     if (rootnodename == "parsererror")         throw("invalid xml structure:\n" + xmlhttp.responsetext);      // getting root element (the document element)     xmlroot = xmlresponse.documentelement;      // testing received xml document expect     if (rootnodename != "response" || !xmlroot.firstchild)         throw("invalid xml structure:\n" + xmlhttp.responsetext);      // value need display child of root <response> element     responsetext = xmlroot.firstchild.data;      // display user message     mydiv = document.getelementbyid("mydivelement");     mydiv.innerhtml = "server says answer is: " + responsetext; } 

my ajax.php file:

<?php     header('content-type: text/xml');     include ("./inc/connect.inc.php");      $username = $_get['username'];     $query = mysql_query("select fname users fname='$username';");     while($row = mysql_fetch_assoc($query)) {         $name = $row['fname'];         if ($name == $username) {                $dom = new domdocument();             $response = $dom->createelement('response');             $dom->appendchild($response);             $text = $dom->createtextnode('username exits');             $response->appendchild($text);             $xml_string=$dom->savexml();             echo $xml_string;         } else {             $dom = new domdocument();             $response = $dom->createelement('response');             $dom->appendchild($response);             $text = $dom->createtextnode('username available');             $response->appendchild($text);             $xml_string=$dom->savexml();             echo $xml_string;         }     } ?> 

this not answer, might give others clue solving problem.

the code snippets op posted appear work expected. php generates xml response , javascript able extract value. way duplicate reported error mangling xml, such adding leading space. op might try adding "ob_end_clean();" statement php part clear response buffer of extraneous output (best guess). , seeing full xmlhttprequest helpful in troubleshooting.

op's code tests name in database , returns 1 of these responses:

match:

<?xml version="1.0"?> <response>username exits</response> 

no match:

<?xml version="1.0"?> <response>username available</response> 

both responses tested feeding them domparse generate xml document:

  var parser = new domparser();   var xmlresponse = parser.parsefromstring( strxml,"text/xml"); 

no errors observed. next, xml fed op's function handleserverresponse(). returned correct value in both cases.