responseXML always NULL and documentElement' of null

I am using Chrome and for debug the Chrome's debugger.

Doesnt matter what iam trying i always get responseXML NULL and ofcourse i got the error "Cannot read property 'documentElement' of null". I am trying to make a searchbar which will put the results in a dropdown menu.

Here is my JS code:

    /*Javascript for search*/

    var xmlHttp = createXmlHttpRequestObject();

    function createXmlHttpRequestObject()                               
    {                                                               
        var xmlHttp;

        if(window.ActiveXObject)
        {
            try
            {                                                       
        xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");   
    }                                                           
    catch(e)
    {                                                   
        xmlHttp = false;                                        
    }                                                       
}else
{   
    try
    {                                                       
        xmlHttp = new XMLHttpRequest();                         
    }                                                           
    catch(e)
    {                                                   
        xmlHttp = false;                                    
    }                                                       
}

if(!xmlHttp)
    alert ("Cant create that object :C");
else
    return xmlHttp;
    }
    function Load()                                                 
    {
        if(xmlHttp.readyState == 0 || xmlHttp.readyState == 4)
        {
            result = encodeURIComponent(document.getElementById('searchBar').value);
            xmlHttp.open("GET","searchQuery.php?searchInput="+result,true);                                                                         
            xmlHttp.onreadystatechange = handleServerResponse;          
            xmlHttp.send(null)                                          
        }else
        {
            setTimeout('Load()',1000);                              
        }
    }
    function handleServerResponse()
    {
        if(xmlHttp.readyState == 4)
        {                               
            if(xmlHttp.status == 200)
            {   
                alert(xmlHttp.responseXML);
                xmlResponse = xmlHttp.responseXML;                  
                xmlDocumentElement = xmlResponse.documentElement;   
                message = xmlDocumentElement.firstChild.data;
                message = message.split(',');
                for(i=0; i<message.length; i++)
                {
                    s += '<li>'+message[i]+'</li>';
                }
                document.getElementById('searchResult').innerHTML= s;
                setTimeout('Load()',1000);
            }else
            {
                alert('Something went wrong!'+xmlHttp.status);
            }
        }
    }
    window.addEventListener('load', Load, false);

And here is my PHP code:

    <?php
    header('Content-Type: text/xml');
    require_once('connect.php');
    $dbc = mysqli_connect(host,user,pw,db) or die ("Error connecting!"); 
    echo '<?xml version="1.0" encoding="UTF-8" standalone="yes" ?>';

    echo '<response>';
        $searchInput = $_GET['searchInput'];
        if($searchInput == ""){ echo "Waiting"; }else
        {
            $queryInsert = "SELECT videoName from videotable WHERE videoName LIKE '$searchInput%' LIMIT 4";
            $queryResult = mysqli_query($dbc,$queryInsert);
            if(!$queryResult){echo "Failed to Query";}else
            {
                $result = "";
                while($row = mysqli_fetch_assoc($queryResult))
                {
                        $result .= $row['videoName'].",";
                }
                echo $result;
            }
        }
    echo '</response>';

    ?>

Still learning XML