Running a Python script from PHP

Question

Tested on Ubuntu Server 10.04. I hope it helps you also on Arch Linux.

In PHP use shell_exec function:

Execute command via shell and return the complete output as a string.

It returns the output from the executed command or NULL if an error occurred or the command produces no output.

<?php 

$command = escapeshellcmd('/usr/custom/test.py');
$output = shell_exec($command);
echo $output;

?>

Into Python file test.py, verify this text in first line: (see shebang explain):

#!/usr/bin/env python

If you have several versions of Python installed, /usr/bin/env will ensure the interpreter used is the first one on your environment's $PATH. The alternative would be to hardcode something like #!/usr/bin/python; that's ok, but less flexible.

In Unix, an executable file that's meant to be interpreted can indicate what interpreter to use by having a #! at the start of the first line, followed by the interpreter (and any flags it may need).

If you're talking about other platforms, of course, this rule does not apply (but that "shebang line" does no harm, and will help if you ever copy that script to a platform with a Unix base, such as Linux, Mac, etc).

This applies when you run it in Unix by making it executable (chmod +x myscript.py) and then running it directly: ./myscript.py, rather than just python myscript.py

To make executable a file on unix-type platforms:

chmod +x myscript.py

Also Python file must have correct privileges (execution for user www-data / apache if PHP script runs in browser or curl) and/or must be "executable". Also all commands into .py file must have correct privileges.

Taken from php manual:

Just a quick reminder for those trying to use shell_exec on a unix-type platform and can't seem to get it to work. PHP executes as the web user on the system (generally www for Apache), so you need to make sure that the web user has rights to whatever files or directories that you are trying to use in the shell_exec command. Other wise, it won't appear to be doing anything.

I recommend using passthru and handling the output buffer directly:

ob_start();
passthru('/usr/bin/python2.7 /srv/http/assets/py/switch.py arg1 arg2');
$output = ob_get_clean(); 

If you want to know the return status of the command and get the entire stdout output you can actually use exec:

$command = 'ls';
exec($command, $out, $status);

$out is an array of all lines. $status is the return status. Very useful for debugging.

If you also want to see the stderr output you can either play with proc_open or simply add 2>&1 to your $command. The latter is often sufficient to get things working and way faster to "implement".

To clarify which command to use based on the situation

exec() - Execute an external program

system() - Execute an external program and display the output

passthru() - Execute an external program and display raw output

Source: http://php.net/manual/en/function.exec.php

Alejandro nailed it, adding clarification to the exception (Ubuntu or Debian) - I don't have the rep to add to the answer itself:

sudoers file: sudo visudo

exception added: www-data ALL=(ALL) NOPASSWD: ALL

In my case I needed to create a new folder in the www directory called scripts. Within scripts I added a new file called test.py.

I then used sudo chown www-data:root scripts and sudo chown www-data:root test.py.

Then I went to the new scripts directory and used sudo chmod +x test.py.

My test.py file it looks like this. Note the different Python version:

#!/usr/bin/env python3.5
print("Hello World!")

From php I now do this:

$message = exec("/var/www/scripts/test.py 2>&1");
print_r($message);

And you should see: Hello World!