如何写php守护进程（Daemon）

<?php 
* 后台脚本控制类 
*/ 
class DaemonCommand{ 
  
  private $info_dir="/tmp"; 
  private $pid_file=""; 
  private $terminate=false; //是否中断 
  private $workers_count=0; 
  private $gc_enabled=null; 
  private $workers_max=8; //最多运行8个进程 
  
  public function __construct($is_sington=false,$user='nobody',$output="/dev/null"){ 
  
      $this->is_sington=$is_sington; //是否单例运行，单例运行会在tmp目录下建立一个唯一的PID 
      $this->user=$user;//设置运行的用户 默认情况下nobody 
      $this->output=$output; //设置输出的地方 
      $this->checkPcntl(); 
  } 
  //检查环境是否支持pcntl支持 
  public function checkPcntl(){ 
    if ( ! function_exists('pcntl_signal_dispatch')) { 
      // PHP < 5.3 uses ticks to handle signals instead of pcntl_signal_dispatch 
      // call sighandler only every 10 ticks 
      declare(ticks = 10); 
    } 
  
    // Make sure PHP has support for pcntl 
    if ( ! function_exists('pcntl_signal')) { 
      $message = 'PHP does not appear to be compiled with the PCNTL extension. This is neccesary for daemonization'; 
      $this->_log($message); 
      throw new Exception($message); 
    } 
    //信号处理 
    pcntl_signal(SIGTERM, array(__CLASS__, "signalHandler"),false); 
    pcntl_signal(SIGINT, array(__CLASS__, "signalHandler"),false); 
    pcntl_signal(SIGQUIT, array(__CLASS__, "signalHandler"),false); 
  
    // Enable PHP 5.3 garbage collection 
    if (function_exists('gc_enable')) 
    { 
      gc_enable(); 
      $this->gc_enabled = gc_enabled(); 
    } 
  } 
  
  // daemon化程序 
  public function daemonize(){ 
  
    global $stdin, $stdout, $stderr; 
    global $argv; 
  
    set_time_limit(0); 
  
    // 只允许在cli下面运行 
    if (php_sapi_name() != "cli"){ 
      die("only run in command line mode\n"); 
    } 
  
    // 只能单例运行 
    if ($this->is_sington==true){ 
  
      $this->pid_file = $this->info_dir . "/" .__CLASS__ . "_" . substr(basename($argv[0]), 0, -4) . ".pid"; 
      $this->checkPidfile(); 
    } 
  
    umask(0); //把文件掩码清0 
  
    if (pcntl_fork() != 0){ //是父进程，父进程退出 
      exit(); 
    } 
  
    posix_setsid();//设置新会话组长，脱离终端 
  
    if (pcntl_fork() != 0){ //是第一子进程，结束第一子进程   
      exit(); 
    } 
  
    chdir("/"); //改变工作目录 
  
    $this->setUser($this->user) or die("cannot change owner"); 
  
    //关闭打开的文件描述符 
    fclose(STDIN); 
    fclose(STDOUT); 
    fclose(STDERR); 
  
    $stdin = fopen($this->output, 'r'); 
    $stdout = fopen($this->output, 'a'); 
    $stderr = fopen($this->output, 'a'); 
  
    if ($this->is_sington==true){ 
      $this->createPidfile(); 
    } 
  
  } 
  //--检测pid是否已经存在 
  public function checkPidfile(){ 
  
    if (!file_exists($this->pid_file)){ 
      return true; 
    } 
    $pid = file_get_contents($this->pid_file); 
    $pid = intval($pid); 
    if ($pid > 0 && posix_kill($pid, 0)){ 
      $this->_log("the daemon process is already started"); 
    } 
    else { 
      $this->_log("the daemon proces end abnormally, please check pidfile " . $this->pid_file); 
    } 
    exit(1); 
  
  } 
  //----创建pid 
  public function createPidfile(){ 
  
    if (!is_dir($this->info_dir)){ 
      mkdir($this->info_dir); 
    } 
    $fp = fopen($this->pid_file, 'w') or die("cannot create pid file"); 
    fwrite($fp, posix_getpid()); 
    fclose($fp); 
    $this->_log("create pid file " . $this->pid_file); 
  } 
  
  //设置运行的用户 
  public function setUser($name){ 
  
    $result = false; 
    if (empty($name)){ 
      return true; 
    } 
    $user = posix_getpwnam($name); 
    if ($user) { 
      $uid = $user['uid']; 
      $gid = $user['gid']; 
      $result = posix_setuid($uid); 
      posix_setgid($gid); 
    } 
    return $result; 
  
  } 
  //信号处理函数 
  public function signalHandler($signo){ 
  
    switch($signo){ 
  
      //用户自定义信号 
      case SIGUSR1: //busy 
      if ($this->workers_count < $this->workers_max){ 
        $pid = pcntl_fork(); 
        if ($pid > 0){ 
          $this->workers_count ++; 
        } 
      } 
      break; 
      //子进程结束信号 
      case SIGCHLD: 
        while(($pid=pcntl_waitpid(-1, $status, WNOHANG)) > 0){ 
          $this->workers_count --; 
        } 
      break; 
      //中断进程 
      case SIGTERM: 
      case SIGHUP: 
      case SIGQUIT: 
  
        $this->terminate = true; 
      break; 
      default: 
      return false; 
    } 
  
  } 
  /** 
  *开始开启进程 
  *$count 准备开启的进程数 
  */ 
  public function start($count=1){ 
  
    $this->_log("daemon process is running now"); 
    pcntl_signal(SIGCHLD, array(__CLASS__, "signalHandler"),false); // if worker die, minus children num 
    while (true) { 
      if (function_exists('pcntl_signal_dispatch')){ 
  
        pcntl_signal_dispatch(); 
      } 
  
      if ($this->terminate){ 
        break; 
      } 
      $pid=-1; 
      if($this->workers_count<$count){ 
  
        $pid=pcntl_fork(); 
      } 
  
      if($pid>0){ 
  
        $this->workers_count++; 
  
      }elseif($pid==0){ 
  
        // 这个符号表示恢复系统对信号的默认处理 
        pcntl_signal(SIGTERM, SIG_DFL); 
        pcntl_signal(SIGCHLD, SIG_DFL); 
        if(!empty($this->jobs)){ 
          while($this->jobs['runtime']){ 
            if(empty($this->jobs['argv'])){ 
              call_user_func($this->jobs['function'],$this->jobs['argv']); 
            }else{ 
              call_user_func($this->jobs['function']); 
            } 
            $this->jobs['runtime']--; 
            sleep(2); 
          } 
          exit(); 
  
        } 
        return; 
  
      }else{ 
  
        sleep(2); 
      } 
  
  
    } 
  
    $this->mainQuit(); 
    exit(0); 
  
  } 
  
  //整个进程退出 
  public function mainQuit(){ 
  
    if (file_exists($this->pid_file)){ 
      unlink($this->pid_file); 
      $this->_log("delete pid file " . $this->pid_file); 
    } 
    $this->_log("daemon process exit now"); 
    posix_kill(0, SIGKILL); 
    exit(0); 
  } 
  
  // 添加工作实例，目前只支持单个job工作 
  public function setJobs($jobs=array()){ 
  
    if(!isset($jobs['argv'])||empty($jobs['argv'])){ 
  
      $jobs['argv']=""; 
  
    } 
    if(!isset($jobs['runtime'])||empty($jobs['runtime'])){ 
  
      $jobs['runtime']=1; 
  
    } 
  
    if(!isset($jobs['function'])||empty($jobs['function'])){ 
  
      $this->log("你必须添加运行的函数！"); 
    } 
  
    $this->jobs=$jobs; 
  
  } 
  //日志处理 
  private function _log($message){ 
    printf("%s\t%d\t%d\t%s\n", date("c"), posix_getpid(), posix_getppid(), $message); 
  } 
  
} 
  
//调用方法1 
$daemon=new DaemonCommand(true); 
$daemon->daemonize(); 
$daemon->start(2);//开启2个子进程工作 
work(); 
  
  
  
  
//调用方法2 
$daemon=new DaemonCommand(true); 
$daemon->daemonize(); 
$daemon->addJobs(array('function'=>'work','argv'=>'','runtime'=>1000));//function 要运行的函数,argv运行函数的参数，runtime运行的次数 
$daemon->start(2);//开启2个子进程工作 
  
//具体功能的实现 
function work(){ 
   echo "测试1"; 
} 
?>