Allowing multiple choices instead of just one

Question

I have a code that is used for adding a channel to an IPTV platform! Currently we have the option to put a channel in single category/genre... What we want to do is instead of this drop box to a have something like checklist or space to write the genres/categories... I have tried everything I remembered I knew, but nothing worked! Thank you

function get_genres() {

    global $tv_genre_id;

    $genres = Mysql::getInstance()->from('tv_genre')->get()->all();

    $option = '';

    foreach ($genres as $arr){
        $selected = '';

        if ($tv_genre_id == $arr['id']){
            $selected = 'selected';
        }
        $option .= "<option value={$arr['id']} $selected>"._($arr['title'])."\n";
    }
    return $option;
}