helpers/KatoBase.php
public static function mergeGet($get, $key, $value) {
        if (array_key_exists($key, $get)) {
            $get[$key]=$value;
        }
        $array = array_merge(array($key => $value), $get);

        return $array;
    }
public static function mergeGet($get, $key, $value) {
        if (array_key_exists($key, $get)) {
            $get[$key]=$value;
        }
        $array = array_merge(array($key => $value), $get);

        return $array;
    }
merges new Get into current url
use it as: url("/model/action", mergeGet($_GET, 'limit', '50'));