Can you create anything in Codeigniter?

[eluser]n0xie[/eluser]
[quote author="Myles Wakeham" date="1253690327"]
But there are weaknesses (mainly in PHP rather than CI). The biggest problem we have encountered is large back-end database processing. [/quote]

That's is why PHP is a frontend language. All 'big' sites who use PHP (youtube, digg, facebook etc) all use it just to generate pages with some logic. The 'back-end' is almost always a language closer to the metal (either Python, C, C++, Java or whatever your particular taste is).

So the question should not be 'can you create anything in CI', but 'can you create anything in PHP', since CI is 'just a framework build on PHP'. If you read the Core files, there is no magic there (meaning there are some clever solutions there but it's not physics). It's just plain PHP.