如何从ajax获取数据? [关闭]

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                    <p class="mb0 mt6">Closed <span title="2018-02-26 13:52:59Z" class="relativetime">2 years ago</span>.</p>
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I am trying to send some data using ajax from file, where I use jQuery UI Sortable to a file which must do something with that data.

In first file ajax start working on stop event:

stop: function(){

        var data = 5
        $.ajax({
            type: "POST",
            data: data,
            url: "ajax.php",
        });
    }

It works perfect, file ajax.php starts to work on every stop event in the first file. But I don't know, how to send a data to ajax.php. If I put in ajax.php this, it's not working:

$filed = "save.txt";
$rez = $_POST['data'];
file_put_contents($filed, $rez);

resume: This post can't be deleted, because it can helps to another users. But single helpful comment, which was a correct answer to a question (by @Jeff), was deleted. Genius logic. Thanks to everybody, have a good fun on your social

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Data needs to be an object.

Example:

stop: function(){
    $.ajax({
        type: "POST",
        data: {name: name, lastname: lastname},
        url: "ajax.php",
    });
}

In case of form could be:

data: $('#form').serialize();