Invoke external shell script from PHP and get its process ID

Question

How can I invoke an external shell script (Or alternatively an external PHP script) from PHP itself and get its process ID within the same script?

Answer 1

For most linux shell tools, it has an option to write the process ID to a file. This is how init.d scripts starts and stops apache or any other service.

For bash, in the script you can use the following to get the PID: $$
You can store it in a file then and then from php check the contents of the file to get the PID.

I am not near a linux box now but if you need more help I can test some code when i am near a linux box.

Answer 2

$command =  'yourcommand' . ' > /dev/null 2>&1 & echo $!; ';

$pid =  exec ( $command, $output );
var_dump($pid);