PHP 获取客户端IP

function getip() {
   static $ip = '';
   $ip = $_SERVER['REMOTE_ADDR'];
   if(isset($_SERVER['HTTP_CDN_SRC_IP'])) {
      $ip = $_SERVER['HTTP_CDN_SRC_IP'];
   } elseif (isset($_SERVER['HTTP_CLIENT_IP']) && preg_match('/^([0-9]{1,3}.){3}[0-9]{1,3}$/', $_SERVER['HTTP_CLIENT_IP'])) {
      $ip = $_SERVER['HTTP_CLIENT_IP'];
   } elseif(isset($_SERVER['HTTP_X_FORWARDED_FOR']) AND preg_match_all('#d{1,3}.d{1,3}.d{1,3}.d{1,3}#s', $_SERVER['HTTP_X_FORWARDED_FOR'], $matches)) {
      foreach ($matches[0] AS $xip) {
         if (!preg_match('#^(10|172.16|192.168).#', $xip)) {
            $ip = $xip;
            break;
         }
      }
   }
   return $ip;
}