Automatically formatting ActionScript with HTML

I am making a website which deals with flash games, (uploading them
for people to play, helping people make them ect.) and part of this
involves people sharing ActionScript code with each other. I have seen
on many websites formatting code automatically like it would be in,
for example, Flash (colour coding, indenting ect).
I've looked around for a PHP script which could parse blocks of
actionscript and format them using HTML, but I haven't been able to
find any. Does anyone know of anything like this? Preferably open
source?
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