php生成唯一ID的四种方法介绍

  echo uniqid();
  echo uniqid();
  echo uniqid();
 OUTPUT:
    5a4b62dd4aeea
    5a4b62dd4aff7
    5a4b62dd4b069

     echo md5(uniqid());
OUTPUT:
    0ac3d6e99b7f5290c93d730eaf9d7d94

public function create_guid($namespace = '') { 
      static $guid = '';
      $uid = uniqid("", true);
      $data = $namespace;
      $data .= $_SERVER['REQUEST_TIME'];
      $data .= $_SERVER['HTTP_USER_AGENT'];
      $data .= $_SERVER['LOCAL_ADDR'];
      $data .= $_SERVER['LOCAL_PORT'];
      $data .= $_SERVER['REMOTE_ADDR'];
      $data .= $_SERVER['REMOTE_PORT'];
      $hash = strtoupper(hash('ripemd128', $uid . $guid . md5($data)));
      $guid = '{' .
          substr($hash, 0, 8) .
          '-' .
          substr($hash, 8, 4) .
          '-' .
          substr($hash, 12, 4) .
          '-' .
          substr($hash, 16, 4) .
          '-' .
          substr($hash, 20, 12) .
          '}';
      return $guid;
     }