php json中文乱码的解决办法

做项目时，网页编码是gbk，ajax请求数据返回json数据时，如果对中文不做处理的话，返回乱码或者根本返回不了值，具体的做法如下。
$return = array();
if(mysql_fetch_array($que)) {
    $sql = "UPDATE $table SET kai = '$kai' WHERE issue = '$issue' ORDER BY id DESC LIMIT 1";
    mysql_query($sql);
    $return['resCode'] = '0000';
    $return['message'] = urlencode(iconv("GB2312","UTF-8//IGNORE",'更新成功'));
} else {
    $return['resCode'] = '0001';
    $return['message'] = urlencode(iconv("GB2312","UTF-8//IGNORE",'更新失败'));
}
echo urldecode(json_encode($return));