ajax onclick方法不起作用

Question

I'm working on Android GCM console that shown all register users and I can send Individual or mass message. My individual message works but cannot handle Ajax to send a mass message. This is my UI code:

$(document).ready(function(){

       $(".send_all").click( function()
       {
            var msg = $(this).parent().find('.txt_message').val();

            $.ajax({
            url: "send_mass_message.php",
            type: 'GET',
            data: {"message": msg},
            beforeSend: function() {

            },
            success: function(data, textStatus, xhr) {
                  $('.txt_message').val("");                  
            }               
            });
       });
    });

UPDATED:

I tested the send_mass_message.php with passing parameters with URL and it works. so my problem is with Ajax part.

send_mass_message.php:

<?php

    if (isset($_GET["message"])) {

        $message = $_GET["message"];


        include_once 'config.php';
        include_once 'db_functions.php';

        $db = new DB_Functions();
        $users = $db->getPURCHASEDUsers();
        $count = mysql_num_rows($users);

        $message = array("message" => $message);
        //echo $message;

        include_once 'GCM.php';
        $gcm = new GCM();

         while($row = mysql_fetch_array($users)){

            $regId = $row["gcm_regid"];
            $registatoin_ids = array($regId);
            $result = $gcm->send_notification($registatoin_ids, $message);
            echo $result;

        }


}

?>