What is the PHP exec() return value?

Question

I am trying to use the PHP exec() function.

If the return_var argument is present along with the output argument, then the return status of the executed command will be written to this variable.

If the execution was successful, it's 0. However, if there is an error, it can be a multitude of other integers. I can't seem to find anywhere what those integers correspond to. How should I interpret the integer that I get?

Update:

I really should have specified this originally, but I am executing another PHP script. Unlike rsync, which has exit values on its man page, I can't find an equivalent for PHP.

So what I am doing is something like:

$rv = exec('php file.php', $out, $rv);

Answer 1

The return value is dependent on the process/program that you ran with exec. For instance, if you ran grep:

The exit status is 0 if selected lines are found, and 1 if not found. If an error occurred the exit status is 2. (Note: POSIX error handling code should check for '2' or greater.)

rsync has about 20 different error exit codes, all painstakingly explained in the man page:

http://linux.die.net/man/1/rsync

so yes, it's program-dependant :)

Even if you're running PHP script, the exit value depends on your program itself. By default php scripts will exit with 0. If you use the exit function you can return different exit codes:

http://php.net/manual/en/function.exit.php

If you want to experimentally determine what your php program exits, call it on the command line:

php file.php

then do

echo $?

this will show you the exit value of your php script.