Maintainability Pitfalls in PHP

Tim Bray makes this prediction about PHP for 2008:

PHP will remain popular but its growth will slow, as people get nervous about its maintainability and security stories.

I share Tim’s love/hate relationship with PHP. It’s definitely a powerful and easy language. But,

… speaking as an actual computer programmer, I really dislike PHP. I find it ugly and un-modular and there’s something about it that encourages people to write horrible code. We’re talking serious maintainability pain.

I’m seeing this right now in some code I’ve recently taken over. The previous programmer was quite skilled and did a great job, but it’s clear there are some areas he had to write quickly and hack together. The flip side of PHP’s ease of use is that sloppiness accumulates very quickly when you’re doing things in a hurry. To some extent, that’s an unavoidable aspect of a growing codebase. But there’s also specific things about PHP itself that foster disorganization and unmaintainability:

* The lack of namespaces. This makes it hard to quickly locate a function or class definition. Classes can be used as namespaces, but that’s a hack, and leads to ugly un-OOPish uses of classes. PHP could really benefit from packages or modules.

* While PHP5 has vastly improved its object functionality, it often feels like the developer culture remains mired in a function-oriented paradigm. PHP’s relative ease of use and wide availability on commodity webhosting has produced a huge pool of developers whose skills are pretty wide-ranging. The low end of that tends towards hacky, function-oriented code that simply “gets the job done.” I’d like to see more thoughtful discussion on PHP sites and forums about object design and philosophy, about when to use functions and classes, and about how to mix them up harmoniously.

* Having a library of thousands of built-in functions in a global namespace with little rhyme or reason to their naming doesn’t exactly provide a great model of maintainability.

* extract() should die. Die, die, die.

* There’s not much agreement about OOP performance: some insist that heavy usage of some OOP features slows PHP down a lot, so you should avoid them whenever possible. Which not only is plain dumb but leads to deliberately confusing and half-assed uses of OOP in the name of better performance.

Maintainability is a matter of discipline, since you can write sloppy code in any language. That aside, PHP does make it extra hard to keep things orderly. I think CakePHP is a step in the right direction, though if you’re going to use a strict MVC architecture, you might as well dump PHP and just go with Ruby on Rails or Python.