Question

its when i starting trying implementing this that i got quite stuck.

some business rules

1 Post can have many Tags.
1 Tag can have many Posts

the database will look like.

• Posts (id, title, body, …)
• Posts_Tags (post, tag)
• Tags (id, tag, …)

when i insert – straightforward

• tags will come from user input as comma separated values
• explode($tags) to get individual tags
• foreach $tag
  • check if tag exists
  • if yes, get id
  • if no, insert tag & get id
• insert post with tags

i am wondering if this is the best way? can i do away with the loop to chk if the tags exists? or simplify it into 1 query?

update a post, abit harder

• how can i check if the user has updated any tags. another loop? but this time there will be some changes (italic)

• explode($tags) to get individual tags

• foreach $tag
  • check if this post has been tagged with this tag
  • if no,
    • does tag exists?
      • yes, get id
      • no, insert and get id
  • if yes, get id
• update post with tags

hmm, … update is more confusing, how will u implement this?

i am using PHP 5.3, Zend Framework 1.10, Doctrine 2

Answer 1

I think the post-tags relationship should be many-to-many; ie: posts have and belong to many tags. This can be implemented with a junction table. Here’s some literature on the subject. Then…

Insert: Do the same thing you are doing now, except you can fetch all tags in one query :

SELECT name FROM tags WHERE name IN ($tags)

Update: The easy way out: Remove all current tags, insert tags as if they were all new. Or…

$tags = explode(',' $_POST['tags']); // remove whitespaces

# delete all current tags that were not included in the edit
DELETE FROM post_tags WHERE post_id=$post_id AND tag_id NOT IN ($tags)

# find out what the current tags are, use a JOIN to find out their labels
SELECT tag_id FROM post_tags WHERE post_id=$post_id
fetch results, remove found tags from $tags, then
foreach new $tag, insert as if they were new