Maintenance Patterns of Large-Scale PHP Web Applications

Scripting languages such as PHP have been criticized as inadequate for supporting maintenance of large-scale software projects. In this paper we attempt to provide insight into the way that five large and well-known PHP applications evolved over time. Several aspects of their history are examined including the amount of unused code, the removal of functions, the use of libraries, the stability of their interfaces, the migration to object-orientation and the evolution of complexity. The results suggest that these systems undergo systematic maintenance which is driven by targeted design decisions and evolution is by no means hindered by the underlying programming language.