Find and replace URLs from [PHP] and [CODE] tags

[ZiNgA BuRgA]

Your regex is extremely weird - I don't know what you were trying to do with it.  It somewhat works on some contrived examples, but probably not what you want, eg

Code:

http://www.example.com

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Also, the 'parse_message' hook is run after MyCodes have been parsed, so trying to do anything to match [code] or [url] tags won't work.
You're probably better off taking the regexes MyBB uses in class_parser.php.