UBBCode: Replaces the ubb tags with HTML, and vice versa

Replaces the UBB tags listed below with HTML tags, and vice versa.
Also keeps the line feeds in the text and removes all HTML tags.

UBB Tags:
[b]...[/b] bold
[i]...[/i] italic
[code]...[/code] source code
[img], [/img] images
[quote]...[/quote] blockquote
[url]http//www.link[/url] links
[url=http//www.link]name[/url] links
[email]me@home.de[/email] email link
[email=me@home.de]name[/email] email link

Additional Tags:
[u]...[/u] underline
[center]..[/center] center
[color=name]...[/color] colors

For a description of ubbcodes see: http://community.infopop.net/infopop/ubbcode.html

FUNCTIONS:
function encode($str)
function decode($str)
function strip($str)
function listCodes()