creating and checking PID

PID.php

    /**
     * @param Integer $pid
     *
     * @return boolean
     */
    public function isProcessRunning($pid)
    {
         if (file_exists("/proc/".$pid)) {
             return true;
         }
         $this->createPIDFile();

         return false;
    }
    
    /**
     * @return Integer
     */
    public function getProcessId()
    {
        return getmypid();
    }
   
    /**
     * @return null
     */
    private function createPIDFile()
    {
        file_put_contents(
            "/home/ubuntu/<project_folder>/cron_pids/myCronPID.txt",
            (string) $this->getProcessId(),
            LOCK_EX
        );
    }