ajax callback function

ajax callback function

why function aSuccess don't work
  1. <?php
    if($_REQUEST['iusername'] != ''){
        echo 'เริ่มต้นเวลา '.date('h:i:s')."\n";
        exit();
    }else{
    ?>
    <!DOCTYPE HTML>
    <html>
    <head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <title>ส่งข้อมุลแบบ post ด้วย jQuery</title>
    <script src="plus/jQuery/jquery.min.js" type="text/javascript"></script>
    <script type="text/javascript">
    /*<!---=-=-=-=-=-=-=-[ jquery api ajax ]-=-=-=-=-=-=-=--->*/
    function aComplete(){    alert('com')
        /* ทำงานทั้งสำเร็จ และมี error */
        $('#blockPreload').removeClass('preload').addClass('preloadHide');
    }
    function aPreload(){
        $('#blockPreload').removeClass('preloadHide').addClass('preload');
    }
    function aSuccess(){
        alert('succ');
    }
    function aShowError(XMLHttpRequest, textStatus, errorThrown){
        alert('jQuery ajax\nstatus = '+textStatus+'\nerror = '+errorThrown+'\nresponse =\n'+XMLHttpRequest.responseText);
    }
    $.ajaxSetup({
        beforeSend:aPreload
        ,cache:false
        ,complete:aComplete
        ,error:aShowError
        ,success:aSuccess
        ,type:'POST'
    });
    $(function(){
        $('#testF').submit(function(){
            data=$('#testF').serialize()
            $.post('jQueryAjax.php' ,data ,function(response){
                //alert(response);
            });
            return false;
        });
    })
    </script>
    <link href="plus/plus.css" rel="stylesheet" type="text/css">
    </head>
    <body>
    <form id="testF" method="post">
      <label for="iusername">รหัสผู้ใช้</label>
      <input type="text" name="iusername">
      <br>
      <label for="ipassword">รหัสผ่าน</label>
      <input type="password" name="ipassword">
      <input type="submit" name="isubmit" value="ส่งข้อมูล">
    </form>
    <div id="blockPreload" class="preloadHide"><img src="plus/images/preload.gif" width="128" height="15" alt="preload"></div>
    </body>
    </html>
    <?php
    }
    ?>