購物網站安裝後進入後台出現 Cannot re-assign $this in

有學員來信問道：購物網站安裝後
進入後台出現 Cannot re-assign $this in :AppServwww wecommerceadminincludesclassesupload.php on line 31
如何處理？
處理方式:
打開
adminincludesclassesupload.php on line 31
將
$this = null;
改成
unset($this);