From the very first line of perldoc -f exec

The "exec" function executes a system command and never returns -- use "system" instead of "exec" if you want it to return.

This would be something like system "some_system_command"; If you need to capture the output from the system command, use backticks: my @output = `system_command`;

You may also want to read about qx which can be found in perldoc perlop.

Edit: The first time I read this, I could have sworn you said your web script was in Perl and you were using exec(). So my note about perldoc -f exec isn't as applicable as I thought, given that your script is actually in PHP. But it's not bad advice, really, just not quite on the mark. *sigh* That's what I get for posting while trying to eat lunch.