php application

I'm a one day old new recruit to Codeigniter and i acknowledge that every day is a learning day so i'll be grateful for any help you may provide.

I have a php application that i want to port to Codeigniter. Would i need to start learning CI or would the same code work. For some part of it anyway, would it be possible to use the source code on individual pages. I understand the templating system in CI as well as the MVC (not very conversant in this, but i have been leaning all i can).

Some code yes and some code no. Not possible to answer in any more detail than that.

You need to read the user guide, as CodeIgntier dosen't work like other frameworks and other frameworks don't work as other frameworks etc.