How to check whether specified PID is currently running without invoking ps from PHP?

Question

We would like to check if a specified process is currently running via PHP.

We would like to simply supply a PID and see if it is currently executing or not.

Answer 1

$pid = 12345;
if (shell_exec("ps ax | grep " . $pid . " | grep -v grep | wc -l") > 0)
{
    // do something
}