获得用户的 IP

function get_clientip(){
    if(isset($_SERVER)){
        if(isset($_SERVER['HTTP_X_FORWARDED_FOR'])){
            $realip = $_SERVER['HTTP_X_FORWARDED_FOR'];
        }elseif (isset($_SERVER['HTTP_CLIENT_IP'])){
            $realip = $_SERVER['HTTP_CLIENT_IP'];
        }else{
            $realip = $_SERVER['REMOTE_ADDR'];
        }
    }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');
        }
    }
    return $realip;
}