?php
class Daemon {
  private $pidfile;
  function __construct() {
    $this->pidfile = dirname(__FILE__).'/daemontest.pid';
  }
  private function startDeamon() {
    if (file_exists($this->pidfile)) {
      echo "The file $this->pidfile exists.\n";
      exit();
    }
    $pid = pcntl_fork();
    if ($pid == -1) {
      die('could not fork');
    } else if ($pid) {
      echo 'start ok';
      exit($pid);
    } else {
    // we are the child
      file_put_contents($this->pidfile, getmypid());
      return getmypid();
    }
  }
  private function start(){
    $pid = $this->startDeamon();
    while (true) {
      file_put_contents(dirname(__FILE__).'/test.txt', date('Y-m-d H:i:s'), FILE_APPEND);
      sleep(2);
    }
  }
  private function stop(){
    if (file_exists($this->pidfile)) {
      $pid = file_get_contents($this->pidfile);
      posix_kill($pid, 9);
      unlink($this->pidfile);
    }
  }
  public function run($argv) {
    if($argv[1] == 'start') {
      $this->start();
    }else if($argv[1] == 'stop') {
      $this->stop();
    }else{
      echo 'param error';
    }
  }
}
$deamon = new Daemon();
$deamon->run($argv);

php deamon.php start

php deamon.php stop