Q:

How to interface PHP front-end with makefile/bash script?

I'm writing a project to manage multiple SSH tunnel via CLI and a web UI. 
Bash script
The service is written in Bash and can:

start a given tunnel or all tunnels,
stop a given tunnel or all tunnels,
status of a given tunnel or all tunnels,
list all tunnels available.

Makefile script
The makefile can do some "administrative" tasks:

add-host add config for a tunnel,
remove-host add config for a tunnel,
etc.

Web UI
I want to create a web interface –using PHP/CodeIgniter–  to control the service.
Question

How can I interface CodeIgniter with makefile and bash command ?
Specifically how do I use exit status to give information to the PHP script ?

A:

PHP's exec (docs here) command will probably do what you need.
You can run your scripts using exec and capture both the output of the script and the exit code. For example:
$output = array();
$exitCode = null;

exec("/path/to/my/script arg1 arg2 2>&1", $output, $exitCode);

$output will be an array of strings - the lines from the script's output. $exitCode will be the exit code returned by the script.
Note, however, that use of exec raises some concerns:

security - you must be careful to ensure that the user of your app cannot execute arbitrary code on your server.
permissions - commands run via exec will be run as the web server user; for Apache on Debian/Ubuntu this will be www-data.

