Php – Possible methods to send the output of a PHP-invoked .exe program (that runs as a separate process, not in PHP) back to the iPhone client

Well the iPhone is able to make HTTP requests, as you will have to do to send the data to your PHP app on the server. In the HTTP response is where you'll put the processed data. You'll want to look at The URL Loading System doc for info on how to use it. The response you get back will be in something like XML or maybe JSON, in which case you can use a 3rd party library.

If you can't do this in one request - for example if your server side processing takes hours - the only way you'll be able to send the data back is with a Push Notification. There's no listening web server that is running on the iPhone that you would be able to send requests to.

Copying my own answer from How do I run a Node.js application as its own process?

2015 answer: nearly every Linux distro comes with systemd, which means forever, monit, PM2, etc are no longer necessary - your OS already handles these tasks.

Make a myapp.service file (replacing 'myapp' with your app's name, obviously):

[Unit]
Description=My app

[Service]
ExecStart=/var/www/myapp/app.js
Restart=always
User=nobody
# Note Debian/Ubuntu uses 'nogroup', RHEL/Fedora uses 'nobody'
Group=nogroup
Environment=PATH=/usr/bin:/usr/local/bin
Environment=NODE_ENV=production
WorkingDirectory=/var/www/myapp

[Install]
WantedBy=multi-user.target

Note if you're new to Unix: /var/www/myapp/app.js should have #!/usr/bin/env node on the very first line and have the executable mode turned on chmod +x myapp.js.

Copy your service file into the /etc/systemd/system.

Start it with systemctl start myapp.

Enable it to run on boot with systemctl enable myapp.

See logs with journalctl -u myapp

This is taken from How we deploy node apps on Linux, 2018 edition, which also includes commands to generate an AWS/DigitalOcean/Azure CloudConfig to build Linux/node servers (including the .service file).