如何将javascript变量传递给另一个php页面

Question

I have a web site that periodically get a message. I put this message in a variable in javascript code (in php file). Then i want to take it in an another php page but doesn't work.

     <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js" type="text/javascript"></script>
<script type="text/javascript" src="jquery-1.9.1.js"></script>


      <!-- Script to import MQTT -->
<script src="https://cdnjs.cloudflare.com/ajax/libs/paho-mqtt/1.0.1/mqttws31.js" type="text/javascript">
</script>

<script>
    ....
    function onMessageArrived(message) {

        console.log("onMessageArrived:" + message.destinationName);
        console.log("message.payloadString:" + message.payloadString);
        if (message.destinationName == "measure") {
            var msg = message.payloadString;
            if (msg.includes("temperature")) {
                //Splitting up the message for the MAC address value

                var MacVal = msg.substring(15,32);
                var mac = String(MacVal);

              $.ajax({
              type: 'POST', 
              url: 'storeData.php', //url to php file
              data: {mac: mac},
              success: function(data)

            });
          }
        }
    </script>

In storeData.php page i have

   $temp = $_POST['mac'];

But this varible is always empty.

Thanks