jQuery ajax not working properly

Question

I'm trying to implement some ajax function in my php website. I basically know how to use jQuery, but for some reason, the returned value is always empty when I alert() it. This is the code I use:

PHP:

if(_POST('ajax'))
{
    $ajax_action = _POST('ajax');
    if($ajax_action == "gwonline")
    {
        return 'test';
    }
}

JS / jQuery:

$.ajax({
    url: './include/ajax.php',
    data: {ajax: 'gwonline'},
    type: 'post',
    success: function(output) {
        alert(output);
    }
});

I debugged it and it does call the file with an ajax request and returns the value, but not received apparently.. What am I doing wrong here? I sincerely don't know..

Answer 1

The response should be pass by echo function, not return . So you must use echo 'test'; instead of return 'test';

Answer 2

不要忘记在PHP中的每个变量前使用$符号。