通过ajax将数据发送到xml类型的php

Question

本主题与其他“ajax to php”主题不同，我在这里使用xml类型的php文件，我想通过ajax将一些数据发送到这个php文件，但是php没有从ajax中检索任何数据。当我删除标题函数时，它从ajax获取数据。这是我的jQuery-ajax代码;

        var borcu_son = $('#borcu').val();
        var borclu = $('#borclu').val();

        if(borcu_son > 0){
            $.ajax({
                url : 'borc_takip_xml.php',
                data : {'borcu_son':borcu_son,'borclu':borclu},
                type: 'post',
                success: function(){
                    alert('send successfull!');
                },
                error: function(){
                    alert('ajax failed!');
                }
            });
        }

和php文件;

<?php 
    header('Content-Type: text/xml;  charset=UTF-8');
    echo '<?xml version="1.0" encoding="UTF-8" ?>';
    echo '<xml>';
?>

<?php ////////////////// BORÇ OLUŞTUĞUNDA BİLGİLERİ AJAXLA AL //////////////////
    if(isset($_POST['borclu']) && isset($_POST['borcu_son'])){
        $borclu = $_POST['borclu'];
        $olusan_borc = $_POST['borcu_son'];

        $borclu_childs = '';

        $borclu_childs .= '<borclu>';
        $borclu_childs .= '<isim>'.$borclu.'</isim>';
        $borclu_childs .= '<tutar>'.$olusan_borc.'</tutar>';
        $borclu_childs .= '</borclu>';

        echo $borclu_childs;
    };

echo '</xml>';
?>