Personal Catalogue: PHP & MySQL — Chapter 5, Exercise 1
====================================================

TASK
Add the tag checkboxes, the "New tag(s)" text input, and the
show/hide JavaScript to your own add_item.php. Add a new book with two
brand-new tags typed into the comma-separated field (tags that don't
exist yet), then confirm both were created in tags and correctly
attached in item_tags.

SOLUTION

With the tags-section markup, the toggleTagsSection() script, and
functions.php's new get_all_tags()/find_or_create_tag()/sync_item_tags()
helpers all wired into add_item.php exactly as shown in the chapter,
submit the form with:

    Type: book
    Title: The Hobbit
    Creator: J.R.R. Tolkien
    New tag(s): Fantasy, Classic Fiction

Since "Fantasy" and "Classic Fiction" don't exist yet in the tags
table, find_or_create_tag() creates both.

Confirm at the mysql> prompt:

    SELECT * FROM tags WHERE name IN ('Fantasy', 'Classic Fiction');

Expected output (ids will differ):

    +----+------------------+
    | id | name             |
    +----+------------------+
    |  5 | Fantasy          |
    |  6 | Classic Fiction  |
    +----+------------------+

Confirm the attachment:

    SELECT items.title, tags.name
    FROM items
    JOIN item_tags ON item_tags.item_id = items.id
    JOIN tags ON tags.id = item_tags.tag_id
    WHERE items.title = 'The Hobbit';

Expected output:

    +-------------+------------------+
    | title       | name             |
    +-------------+------------------+
    | The Hobbit  | Fantasy          |
    | The Hobbit  | Classic Fiction  |
    +-------------+------------------+

WHY THIS WORKS AS AN ANSWER
----------------------------
It exercises the genuinely new-tag path specifically (rather than
picking from an existing checkbox, which wouldn't test
find_or_create_tag() at all), and verifies both halves of the real
outcome — the tags rows were actually created, and the item_tags rows
correctly link them to the new book — rather than just trusting the
UI looked right.