phpBB 3.1 extension, that adds the ability to tag topics with key words.

• add tags when posting a new topic
• Tag suggestions based on existing tags
• edit tags when editing first post of topic
• SEO-optimization: tags are added to meta-content keywords in viewtopic
• tags are shown in viewforum (can be disabled in acp)
• enable tagging of topics on a per forum basis
• Responsive layout
• Full UTF-8 support

• search topics by tag(s)
• /tag/{tags}/{mode}/{casesensitive} shows topics tagged with all (mode=AND, default) or any (mode=OR) of the given tags, where tags are comma separated tags and casesensitive can be true to search case-sensitive or false (default), e.g.:
  • /tag/tag1,tag2/OR lists topics that are tagged with tag1 OR tag2 OR tAG2
  • /tag/tag1,tag2/AND lists topics that are tagged with [tag1 AND (tag2 OR tAG2)]
  • /tag/tag1,tag2 lists topics that are tagged with [tag1 AND (tag2 OR tAG2)] (mode=default=AND, casesensitive=default=false)
  • /tag/tag1,tAG2/AND/true lists topics that are tagged with (tag1 AND tAG2)

• /tags shows a tag cloud
• acp option for tag cloud to be displayed on board-index or not
• acp option to limit count of tags shown in tag cloud on the index page
• dynamic tag-size in tag cloud depending on its usage count
• acp option to en/disable display of usage count of tags in tag cloud

• configure a regex to decide which tags are valid and which are not
• maintenance functions in ACP -> Extensions -> RH Topic Tags
• Whitelist
• Blacklist
• User and Mod+Admin permission for who can add/edit RH topic tags
• spaces in tags are converted to "-" by default (you can disable it in ACP)
• Manage existing tags in ACP
  • Delete tag
  • Rename tag
  • Merge tags (rename one tag to the same name as another tag and they will automatically be merged )

Clone (or download an move) the repository into the folder phpBB3/ext/robertheim/topictags:

cd phpBB3
git clone https://github.com/RobertHeim/phpbb-ext-topictags.git ext/robertheim/topictags/

Go to ACP -> tab Customise -> Manage extensions -> enable RH Topic Tags Go to ACP -> Forums -> edit/create any forum -> set Enable RH Topic Tags to Yes

Goto ACP -> Extensions -> RH Topic Tags

Go to ACP -> tab Customise -> Manage extensions -> disable RH Topic Tags

cd phpBB3/ext/robertheim/topictags
git pull

Go to ACP -> tab Customise -> Manage extensions -> enable RH Topic Tags

https://www.phpbb.com/community/viewtopic.php?f=456&t=2263616