Contract: protecting code or not?

I just started a project for which I need to do both database design and some original programming work. My client would like to draw up an agreement that specifies what usage is permissable for the code I develop. Apparently one of the staff people thought that if the program is very cool (it had better be, but it will be a lot of work!) they could resell it, and my client said she thought that was not right. I'm doing this in PHP - so I'll be using some code snippets of my own, some open source libraries, and doing some original development. It would seem to me that it's ok for my client to reuse some of my code, in the spirit of open source? But that it wouldn't be right to resell the whole product. So my qustions are: (1) How do you all define this (2) Where can I find wording to say what I need that will protect my work. (3) I want to include a confidentiality agreement stating that all data from her DB will remain private. - need wording for that too! Anne