Producing code that clearly conveys a developer's intent is key to any well written application. That not only applies to PHP, but every programming language. Developers who emphasize the creation of legible code tend to create applications which are easier to both maintain and expand upon. After seven years of programming in PHP I've worked on a variety of projects where well organized and legible code were set aside for numerous reasons. Some of those reasons include time constraints, lack of experience, lost enthusiasm, misdirected pre-optimizing, and the list goes on.