Im trying to send a js variable value to php using ajax. So when the page loads, it will do the job, at the same url. Im trying this but nothing seams to work:

*<script>
    $(document).ready(function() {


    var postID = 5;
    $.ajax({
        type: "POST",
        url: '',
        data: "userID=" + postID,
        success: function(data)
        {
            alert("success!");
        }
    });
});

</script>


<?php
$postID = (isset($_POST['postID'])) ? $_POST['postID'] : 0;
if($postID==0) {
    echo 'User ID not found';
}
?>*