What is the problem with Ajax (jQuery) And Php ? Why my code does not work ?

jQuery Kod:

$(document).ready(function(){   

    $.ajax({
    type: "GET",
    url: "Tags.php",
    dataType: "xml",
    success: function(xml) {
    alert("success");
    }
    }); 

});

Tags.php Kodu

<?xml version="1.0" encoding="UTF-8"?>
<tages>
<?php echo "<tag>hello</tag>"; ?>
</tages>