This function is ideal for checking if a given process is running, I have seen solutions that involve running the system utilites like PS and parsing the answer, which should work fine, but this allows you to check a given PID with a single callfunction CheckPID( $PID ){ // Check if the passed in PID represents a vlaid process in the system // Returns true if it does // Turn off non-fatal runtime warning for a moment as we know we // will get one if the PID does not represent a valid process $oldErrorLevel = error_reporting(0); error_reporting( $oldErrorLevel & ~E_WARNING ); $res = pcntl_getpriority($PID); error_reporting( $oldErrorLevel); return ! ( $res === false);}