A small team and I are tasked with developing a web site. The client has referenced a particular open source project (we'll call it X) when describing some of the features. Because of this, the team wants to start with X and adapt it to satisfy the client. I have looked at X and its code and, in my opinion, it would be unwise. However, my experience is limited, and could really benefit from the insights of others so that I can figure out what I should be asserting as the right direction for the team.
My red flags are going up and this is why. X was developed in the earlier days of PHP; 500 line blocks of code are the norm; global variables are abundant; giant switch cases are the norm for switching between which page is shown. There is no clear mapping between URL and where the code for that page sits. From a feature-set standpoint, X is actually software specialized for a different task and has dozens of features we don't need or have use for that come as core assumptions. We will be unable to adapt X through its plugin system.
That said, there are a few features which can be mapped, with some modification, to suit our purposes. I believe this is the attraction the team feels.
I would feel comfortable if, instead of using X directly, we lifted what is salvageable and useful to us. We can then use that code, and the same 3rd party libraries X is using, in a new code base built on top of a PHP web framework (particularly Agavi, so you understand what I mean by 'web framework'). The web framework gives us a strong MVC structure and provides the common facilities for web development, or adapters to work with 3rd party libraries that do so. We will also have a clean slate feature-wise to work from, which means we can work additively instead of subtractively. Because the code base is better structured, and contains none of what we don't need, it will be easier to document, which is a critical requirement of our client.
So to summarize, the team wants to use X, whereas I want to take the bits we can from X and use a web framework instead. I want to bounce this opinion off of other's experiences so that I can be more informed.