PHP code run multiple time on single submit - php

Question

Background: I have implemented the GCM enable android app which is use to received announcement and the announcement are send by a web site developed in php where we have created a html for m to enter the annoncement and button to submit.We submit this to php file which call the which get the all the registered user and run the code to send the message to all the user.
<?php
include_once 'db_functions.php';
include_once 'gcm.php';
$gcm = new GCM();
$db_functions = new DB_Functions();
$alluser = $db_functions->getAllUsers();
$message = array("price" => $message);
ob_start();
while ($row = mysqli_fetch_assoc($alluser)) {
echo "\n" . $row["name"] . "--";
$result = $gcm->send_notification(
array($row["gcm_regid"]),
$message);
echo $result;
}//End of while statement
?>
Issue: When I submit the form to send message to android app by using GCM call the same php webpage run for multiple time which is causing duplicate messages in client android app.
Could any one help me understand or provide me link which discuss this issue.
Possible Issue may be as the number of users have increase and it take a long time run this code for each use.
Any help in optimizing will be greatly appreciated.

Answer 1

I don't know what GCM library you use, but note that you can also call GCM with a list of ID's (up to 1000) to send the same message. So in that way you don't need to make 1000 calls if you have 1000 users. Unless of course your message is different for each user, but it doesn't look like it.
Besides that I don't think there is something wrong with your code. It can be that it takes a long time and people submit the form twice. Or you have some javascript on the button to submit the form which makes it to submit twice?

Answer 2

Thanks for your comment.
Basically i have found that this issue was due to the browser refresh in on the send message php page when network was week(lollipop network issue) so it cause the same message to be send for multiple no of time.
To solve the issue I have redesign the PHP page i.e. form to accept the message and send message by using the concept of request redirect get concept.
The link for the your reference.
https://en.wikipedia.org/wiki/Post/Redirect/Get
So that this issue does not happen due to refreshing.
Also thanks Jorgen for pointing out the concept of sending request to gcm server for all the gcm registration id it has improve the performance.