/*
 * 同一個(gè)PHP進(jìn)程只運(yùn)行一次，根據(jù)進(jìn)程名字判斷是否為排重進(jìn)程，只能運(yùn)行于linux，高并發(fā)條件下是并發(fā)安全的。
 */

class SyncProcess {

 private $pidFile;

 function __construct($pidFile) {
  $this->pidFile = $pidFile;
 }

 /**
  * 非阻塞方式返回進(jìn)程是否正在運(yùn)行
  */
 function check() {
  if (PHP_OS == 'Linux') {
   $pidFile = $this->pidFile;
   if (!empty($pidFile)) {
    $flag = false;
    $pidDir = dirname($pidFile);
    if (is_dir($pidDir)) {
     $flag = true;
    }
    if ($flag) {
     $running = true;
     clearstatcache(true, $this->pidFile);
     if (!file_exists($this->pidFile))
      file_put_contents($this->pidFile, '', LOCK_EX);
     $f = fopen($this->pidFile, 'r+');
     if (flock($f, LOCK_EX ^ LOCK_NB)) {
      $pid = trim(fgets($f));
      if (!$this->is_process_running($pid)) {
       $running = false;
      }
     }
     if (!$running) {
      fseek($f, 0);
      ftruncate($f, 0);
      fwrite($f, getmypid());
     }
     flock($f, LOCK_UN);
     fclose($f);
     return $running;
    } else {
     debug_print("pid file($pidFile) is invalid", E_USER_WARNING);
    }
   } else {
    debug_print("pid file cant't be empty", E_USER_WARNING);
   }
  } else {
   debug_print(__CLASS__ . ' can only run in Linux', E_USER_WARNING);
   return true;
  }
 }

 /**
  * 如果正在運(yùn)行或者發(fā)生未知錯(cuò)誤返回true，如果沒(méi)有運(yùn)行返回false
  * @param mixed $pid
  */
 private function is_process_running($pid) {
  if (is_numeric($pid) && $pid > 0) {
   $output = array();
   $line = exec("ps -o pid --no-headers -p $pid", $output);
   //返回值有空格
   $line = trim($line);
   if ($line == $pid) {
    return true;
   } else {
    if (empty($output)) {
     return false;
    } else {
     if (php_sapi_name() == 'cli')
      $n = "\n";
     else
      $n = "<br>";
     //到這一步的話(huà)應(yīng)該是出什么問(wèn)題了
     $output = implode($n, $output);
     debug_print($output, E_USER_WARNING);
     return true;
    }
   }
  }else {
   return false;
  }
 }

}