PHP 获取用户的真实IP

 /** * 获得用户的真实IP地址 * * @access public * @return string */ /**
* 获得用户的真实IP地址
*
* @access public
* @return string
*/

public static function real_ip()
{
   static $realip = NULL;
   
   if ($realip !== NULL)
   {
      return $realip;
   }
   
   if (isset($_SERVER))
   {
      if (isset($_SERVER['HTTP_X_FORWARDED_FOR']))
      {
         $arr = explode(',', $_SERVER['HTTP_X_FORWARDED_FOR']);
         
         /* 取X-Forwarded-For中第一个非unknown的有效IP字符串 */
         foreach ( $arr as $ip )
         {
            $ip = trim($ip);
            
            if ($ip != 'unknown')
            {
               $realip = $ip;
               
               break;
            }
         }
      }
      elseif (isset($_SERVER['HTTP_CLIENT_IP']))
      {
         $realip = $_SERVER['HTTP_CLIENT_IP'];
      }
      else
      {
         if (isset($_SERVER['REMOTE_ADDR']))
         {
            $realip = $_SERVER['REMOTE_ADDR'];
         }
         else
         {
            $realip = '0.0.0.0';
         }
      }
   }
   else
   {
      if (getenv('HTTP_X_FORWARDED_FOR'))
      {
         $realip = getenv('HTTP_X_FORWARDED_FOR');
      }
      elseif (getenv('HTTP_CLIENT_IP'))
      {
         $realip = getenv('HTTP_CLIENT_IP');
      }
      else
      {
         $realip = getenv('REMOTE_ADDR');
      }
   }
   
   preg_match("/[\d\.]{7,15}/", $realip, $onlineip);
   $realip = !empty($onlineip[0]) ? $onlineip[0] : '0.0.0.0';
   
   return $realip;
}