问使用内容类型Application/json的AJAX调用不从PHP检索数据

EN

    var formData = {"data1" : a, "data2" : b, "data3" : c};

    $.ajax({
        dataType: "json",
        contentType : "application/json; charset=UTF-8",
        url: '/getjson.php',
        data : formData,
        success: function(response) {
            CurrentArray = response;
        }
    });

<?php
//select webpage to get JSON from
switch ($_GET['data1']){
    Case 1: 
        $result = get_with_curl($webpage1);//select webpage 1
    break;

    Case 2: 
        $result = get_with_curl($webpage2);//select webpage 1
    break;
}
echo $result['FILE'];
?>