官网的收费，所以自己下载了个英文包language文件夹，和默认的简体中文的语言包，来实现切换
1.在/source下增加目录locale,将待切换的语言包langguage放到里面并重命名，下面以中文包更名为zh_CN,英文包更名为en_US为例进行操作(原先默认的/source/language还留在那里一份，与页面无关的继续调用默认的就可以)
2.在/source/class/class_core.php底部引入文件：
/**begin 多语言包切换**/
require_once './source/discuz_locale.php';
/**end 多语言包切换**/
3.在/source下增加文件discuz_locale.php,内容是
<?php
if(!defined('IN_DISCUZ')) {
exit('Access Denied');
}
empty(getcookie('locale')) ? dsetcookie('locale','zh_CN') : '';
if(isset($_GET['lang'])){
$mylang = array(
'cn' => 'zh_CN',
'en' => 'en_US'
);
if(array_key_exists($_GET['lang'], $mylang)){
dsetcookie('locale',$mylang[$_GET['lang']]);
}
}
define('DISCUZ_LOCALE', DISCUZ_ROOT.'source/locale/'.getcookie('locale'));
4./source/function/function_core.php中的checktplrefresh方法中，这两个if里加上 '1 ||',
来关闭缓存，这是为了切换语言后前台页面能立即生效，而不必去后台更新缓存。
if(1 || empty($timecompare) || $tplrefresh == 1 || ($tplrefresh > 1 && !($timestamp % $tplrefresh))) {
if(1 || empty($timecompare) || @filemtime(DISCUZ_ROOT.$subtpl) > $timecompare)
5.替换/source/function/function_core.php，source/class/optimizer/optimizer_setting.php中包含有language/的加载路径，替换成DISCUZ_LOCALE。如
include DISCUZ_LOCALE.($path == '' ? '' : '/'.$path).'/lang_'.$file.'.php';
6.前台增加切换按钮，分别加上链接 http://url?lang=cn 和 http://url?lang=en就可以
<td> <a href="javascript:changetoVersion('cn','en')" class="xi2 xw1">中文版</a></td>
<td> <a href="javascript:changetoVersion('en','cn')" class="xi2 xw1">English</a></td>
<script>
function changetoVersion(arg1,arg2){
if(location.href.indexOf('?lang=') != '-1' || location.href.indexOf('?') == '-1'){
arg1 = '?lang=' + arg1;
arg2 = '?lang=' + arg2;
}else{
arg1 = '&lang=' + arg1;
arg2 = '&lang=' + arg2;
}
if(location.href.indexOf(arg1) != '-1'){
location.reload();
}else if(location.href.indexOf(arg2) != '-1'){
location.href = location.href.replace(arg2,'')
+ arg1;
}else{
location.href += arg1;
}
}
</script>
思路有借鉴,感谢：http://tieba.baidu.com/p/3600965400
以下是英语包：discuz3.2_language_en.zip