Additions to a PHP driven website

We need to add some more logic into an existing PHP driven website. This may end up in a long term partnership this is why details have been omitted. The succesful bidder should be able to provide formally documented functional specifications after the analysis of requirements, there maybe a need to create unit tests before the development and be able to work to tight deadlines. Quality of code is paramount for this project. You will be required to sign an NDA before specific details of the project can be sent out.