[函数]获取真实IP地址

获取真实IP地址函数封装，这个用的应该会非常多

function getIp(){
   $onlineip='';
   if(getenv('HTTP_CLIENT_IP')&&strcasecmp(getenv('HTTP_CLIENT_IP'),'unknown')){
       $onlineip=getenv('HTTP_CLIENT_IP');
   } elseif(getenv('HTTP_X_FORWARDED_FOR')&&strcasecmp(getenv('HTTP_X_FORWARDED_FOR'),'unknown')){
       $onlineip=getenv('HTTP_X_FORWARDED_FOR');
   } elseif(getenv('REMOTE_ADDR')&&strcasecmp(getenv('REMOTE_ADDR'),'unknown')){

       $onlineip=getenv('REMOTE_ADDR');
   } elseif(isset($_SERVER['REMOTE_ADDR'])&&$_SERVER['REMOTE_ADDR']&&strcasecmp($_SERVER['REMOTE_ADDR'],'unknown')){
       $onlineip=$_SERVER['REMOTE_ADDR'];
   }
   return $onlineip;

}