echo getip();

function getip(){
    if (isset($_SERVER["HTTP_CLIENT_IP"]) && $_SERVER["HTTP_CLIENT_IP"] && strcasecmp($_SERVER["HTTP_CLIENT_IP"], "unknown")){
        $ip = $_SERVER["HTTP_CLIENT_IP"];
    }elseif(isset($_SERVER["HTTP_X_FORWARDED_FOR"]) && $_SERVER["HTTP_X_FORWARDED_FOR"] && strcasecmp($_SERVER["HTTP_X_FORWARDED_FOR"], "unknown")){
        $ip = $_SERVER["HTTP_X_FORWARDED_FOR"];
    }elseif(isset($_SERVER['REMOTE_ADDR']) && $_SERVER['REMOTE_ADDR'] && strcasecmp($_SERVER['REMOTE_ADDR'],"unknown")){
        $ip = $_SERVER['REMOTE_ADDR'];
    }else{
        $ip = "unknown";
    }
    $arr=explode(",",$ip);
    if(count($arr)>0){
        $ip=$arr[0];
    }
    if(preg_match('/^((?:(?:25[0-5]|2[0-4]\d|((1\d{2})|([1-9]?\d)))\.){3}(?:25[0-5]|2[0-4]\d|((1\d{2})|([1 -9]?\d))))$/',$ip) && strlen($ip)<=15){
        return $ip;
    }else{
        return 'unknown';
    }
}