In the course chapter "File Uploading and List Paging Display",

1. queries the article list. $artList is defined in the if judgment to determine whether cate_id exists. Then give The code for template assignment should be displayed as undefined.
   

2. When judging whether cate_id exists, if it exists, the condition will include cata_id = the incoming cate_id, but the query for querying all files is directly added outside the judgment. I feel it should be After including the cate_id query, you should also query all articles.