fuelphp validation rules

<?php

class ValidateRules
{

    static private $folderName = 'rules';


    /**
     * get external validation rules and instance of Validation() object
     *
     * @name name of file rules or send array of validate rules
     * @name instanceName name of instance Validatio::forge()
     *
     * @return instance of Validation::forge()
     */
    public static function getRules($name, $instanceName = null)
    {
        if($instanceName)
        {
            $instance = \Validation::forge($instanceName);
        } else {
            $instance = \Validation::forge(\Str::random());
        }

        $fileName = explode('_', $name);

        $file = APPPATH. DS .$fileName[0]. DS .self::$folderName. DS .$name.'.php';

        $rules = include($file);

        $debug = '';

        foreach($rules as $field => $item)
        {
            $instance->add_field( $field, $item['label'], self::convertToString($item['rules']) );
        }

        return $instance;
    }


    /**
     *
     * @return string
     */
    private static function convertToString($rules = array())
    {
        $string = '';
        foreach($rules as $name => $rule)
        {

            if(is_array($rule))
            {
                $string .= $name.'[';
                $string .= implode(',', $rule);
                $string .= ']|';
            }
            elseif($name == $rule)
            {
                $string .= $rule . '|';
            } else {
                $string .= $name.'['.$rule.']|';
            }

        }

        $string = trim(rtrim($string, '|'));

        return $string;
    }


}