Post data not showing at the process script.

Post data not showing at the process script.

I've been having great difficulty with this simple script. From every thing I've read this should work.

$(document).ready(function(){
    $(".add_to_profile").css("background-color", "yellow");
    $('a.bookmark').click(function (){
        var addedbookmark = function (data) {
           
            var divreturn = 'div.return-'+ data.nid;
            var divbookmark = 'div.bookmark-'+ data.nid;
            $(divreturn).html("bookmark added");
            $(divbookmark).html('<a href="remove_bookmark/'+ nid+'" class="bookmark">Remove Bookmark</a>')
            $(divreturn).html(nid );
        }
        $.ajax(this.href,
        {
            type : 'POST',
            dataType : 'json',
            success : addedbookmark,
            data : "js=1",
        });
 //       return false;
    });
});

The important data is sent as a get, and works fine,  but I need the post to signal that jQuery sent the data.

<?php
var_dump($_POST);
die;
header('Content-type: application/json');

echo json_encode (array(
            'success' => 'added to profile',
            'nid' => 95,
        ));
exit();

All I get is:
array
empty


It would be great if someone could give me a clue.