Replace content within post, signature, conversation?

[HappyWorld]

How to do content replacement within post, signature, conversation?
I'd like to make my own regular expression to replace content.

Thank you

 

[Jeremy]

Permanently? Temporary? When is this occurring?

 

[HappyWorld]

Permanently? Temporary? When is this occurring?

temporary is fine (which means if i disable the plugin code, all will go back to the original string).
But if it is permanent (which means the replacement happens before the content is saved to database), it is fine too.

It is a kind of "censoring" (which is replacing pre defined "bad words" by asterisks).
But i want to replace something (pre defined by regular experssion) to something else (not asterisks).

It occurs when it is viewed.

 

[HappyWorld]

Nvm i think i can learn from this resource
https://xenforo.com/community/resources/keyword-replace-by-waindigo.635/

and maybe this too (if needed)
https://xenforo.com/community/resources/*******-auto-link-replacer.1529/