nginx - php基础问题。。

某个项目的文件

sqlite();
        $tLCount = $tSqlite->getRow("SELECT COUNT(0) c FROM sqlite_master where type='table' and name='lang'");
        $tLang = array();
        if(!empty($tLCount['c'])){$tLang = $tSqlite->getRow($tSql = 'select * from lang');}
        
        $tLang = empty($tLang['lang'])?'cn':$tLang['lang'];
        include realpath(dirname(__FILE__).'../../../lang/'.$tLang.'/common.php');
        $lang = json_encode($lang);
        $lang = json_decode($lang);
        $this->assign('lang' , $lang);
        $this->assign('l' , $tLang);
        $this->l = $tLang;
        $this->lang = $lang;
        //(1 & $this->_auth) && $this->_session();
        //(1 < $this->_auth) && $this->_role();
        $tSqlite->close();
    }

问题一：

        $lang = json_encode($lang);
        $lang = json_decode($lang);

这两句在这里什么作用？，为什么要把$lang变成json格式后又解析成php变量？这不是多此一举么？
问题二：

        $this->assign('lang' , $lang);
        $this->assign('l' , $tLang);
        $this->l = $tLang;
        $this->lang = $lang;

这四句又怎么理解？
我的理解是assign的第一个参数是变量名，后面是它的变量值，可是

`$this->l = $tLang;`不就是将`$tLang`赋值给`$this`的`l`属性么？这四句不就重复了么？