Run a php script for so long in background in heroku - php

Question

I have a PHP script which sends messages to a list of users, which I hosted in Heroku. Now I wanted to add a delay in between those messages. Say like, 6 mins gap between each message. So if there are 90 users, that script should run for 9 hours, in the background.
I tried calling this script using ajax, so it runs in the background and adding sleep(360); inside the for loop, to get 6 mins delay. But it only works for approx 10 to 20 users, after that it stops.
foreach ($users_list["users"] as $key => $value) {
try{
....
code for sending message
.....
}catch(Exception $e){
continue;
}
sleep(360);
}
So I would like to know, what is the optimal way to achieve this, in Heroku.

Answer 1

Calling a script using AJAX doesn't call it in the "background" it just runs it Asynchronously from the page you are on. In other words it's still running in Apache, has any session data, and still bound by the timeout settings of PHP and Apache.
To run it truly in the background you can use something like CRON
Or if you are allowed to on your server you can call it by command line like with exec or shell_exec, there are a few other similar functions too, such as popen, system etc. They all do things in a slightly different way.
Some environmental stuff will be different and this may have a big impact on your code. For example a lot of stuff in $_SERVER is not set or has different information. Such as the servers IP address may not be in there, you won't have any session stuff. You won't be able to use $_GET or $_POST but can get the input data (form the command line call) from the $argv array, the first item being the files path... etc...
Basically you need to call it like this:
exec('php -f "path/to/php/file.php" "arg1" "arg2"');
Calling it this way it will still be blocking, meaning it waits for execution of the called script.
To go one step further and make it non-blockin you can add (on Linux)
exec('php -f "path/to/php/file.php" "arg1" "arg2" > /dev/null &');
The & at the end is the most important bit.
Now on Windows it's a bit of a different ballgame. I've had success using this
$WshShell = new \COM('WScript.Shell');
$cmd = 'cmd /C php "path/to/php/file.php" "arg1" "arg2"';
$WshShell->Run($cmd, 0, false);
Also on windows to run PHP with just php you have to add the path to the php.exe yhou want to use to the path environmental variable. Otherwise you have to use the full path to the exe instead of just php
In either case you should be very careful about putting end user data in any command line call. There are 2 functions to sanitize it, but I try to just not put it in.
escapeshellarg
escapeshellcmd
I wrote a wrapper class for this you can find on my GitHub
Hope it helps.