PIDChecker.php

<?php
/**
 * php PID checker class for linux, using /proc/$PID/ for is-alive-check
 *     $pidchecker = new PIDChecker("/tmp/boku_accman_set_boku_mailbox.pid");
 *     try {
 *         $pidchecker->check();
 *     } catch(Exception $e) {
 *         print($e->getMessage())."\n";
 *         die();
 *     }
 **/
class PIDChecker {
	protected $pidfile = null;
	public function __construct($pidfile) {
		$this->pidfile = (string)$pidfile;
	}
	protected function getOtherPid() {
		return trim(file_get_contents($this->pidfile));
	}
	protected function shouldStopExecution() {
		$stop_execution = false;
		if (file_exists($this->pidfile)) {
			$pid = $this->getOtherPid();
			$stop_execution = file_exists('/proc/'.$pid);
		}
		return $stop_execution;
	}
	/**
	 * Check if another process is locking the PID file. If so throws an 
	 * Exception.
	 *  
	 * @throws Exception
	 */
	public function check() {
		if($this->shouldStopExecution()) {
			throw new Exception(sprintf("PID file already exists and PID job is still running (PID: %d)", $this->getOtherPid())); 
		} else {
			$success = @file_put_contents($this->pidfile, getmypid()."\n");
			if(($success === false) && (sfConfig::get('sf_environment') == "prod")) {
				throw new Exception("Could not create pidfile. ");
			}
		}
	}
}