Need library to create TAGS

[iamvela]

I am looking for an open source library that will allow me to add tags to my web property. I am talking about not just the generation of the clouds, but also the creation of the tags, the ability to recognize same tags by multiple users, and to correlate the underlying content...

Ideally I'd like for this library to be be PHP/AJAX so that it does things like auto-complete for a user, manages case insensitivity, plurals, and a variety of other issues.I'm looking for an open-source piece that already has the sophistication built into it.

Questions:
- Do you know of one?
- which one?
- are you using one?
- do you like the one you are using?
- any recommendations?
- any gotchas?
- any bad experiences?

Please share, thanks. I hope my question is clear, if not I'd be happy to post clarifications. Regards,

[rogerd]

Will users be able to add their own tags? On one site, there were no preloaded tags but users could add tags. As they type, it auto-suggests completions from the tags set up previously.

I don't know of a tag library. It seems like it might need to be topical depending on the subject of your site.

[iamvela]

Yeah, users should be able to add their own tags.

I've never seen "topical" that's what tags are themselves e.g. Social Bookmarking: you create your own tags!