URL redirection in php for Opera Mini browser

Question

I want to redirect URLs clicked in opera mini to a certain browser using PHP. I am working on that and this is my code so far:

if(! empty($_SERVER['HTTP_USER_AGENT'])){
    $useragent = $_SERVER['HTTP_USER_AGENT'];
    if(preg_match('@(Opera Mini)@', $useragent)){

        $host = $_SERVER['REQUEST_URI'];

        if($host !== 'mywebsite.com/browser-error'){
            header('Location: ./browser-error');
        }
    }
}

Can someone help me do this?