lang.file // this file is also shared by other applications
=========

<?php
$lang = 'en';

function lang($phrase) {
    global $lang;
    static $trans = array(

// language option
        'en' => array('ENG','ENG','ENG'),
        'zh' => array('繁體','繁體','繁體'),
        'cn' => array('簡體','簡體','簡體'),
        'pdmcat' => array('Brands','品牌','品牌')
    );

    if (array_key_exists($phrase, $trans)){
        switch ($lang) {

        case 'en':
        return $trans[$phrase][0];
        break;

        case 'zh':
        return $trans[$phrase][1];
        break;

        case 'cn':
        return $trans[$phrase][2];
        break;

        default:
        return '???';
        break;
        }

    }
};

==========
controller.php

<?php
require_once(PATH . '/lang.file');

class MyClass {

    public function translate($phrase) {
        return call_user_func('lang',$phrase);
    }

}

$test = new MyClass($lang);
echo $test->translate('pdmcat');