It happens frequently that you have mutually independent and exclusive tasks at hand. The principle of software engineering always advocates against grouping tasks together—modularity is the correct name of the phenomenon advocated. So is the case with you and Phing. What if you have a number of tasks to be undertaken? There are two routes to choose from: shorter and longer. The shorter way leads you to quick results but your friend, software engineering, will be offended. The longer way can irritate you at first, but dear friend, it would let you get more close to software engineering.

A wise decision is to befriend software engineering and take the longer route. Thus, you will create individual build files for individual tasks. Beware, though. Deciding the grouping of tasks in itself is a double-edged sword—it cuts both ways.