I have been using PHP1 as my primary language for five months now so I feel somewhat qualified to speak about it. My overall conclusion is that PHP is weak sauce. It is easy to get started with PHP but it’s usefulness decreases as the complexity of the application increases. This is primarily because keeping PHP code maintainable requires unnatural levels of discipline. Choosing PHP for a greenfield project is a technical risk that is unnecessary in today’s rich web application ecosystem. Of course, most projects aren’t greenfield so there are plenty reasons to have PHP around.
I find PHP to be a deeply frustrating environment in which to work. It seems to have occurred, as opposed to designed or even evolved, without much of an overarching vision. In “The Mythical Man-Month” Fredrick Brooks claims that “conceptual integrity is the most important consideration in system design”. Unfortunately, PHP has very weak conceptual integrity. It seems mostly to be a collection of decisions that seemed expedient at the time with little thought about how that would impact the over all system.
I remember hearing a few years ago about PHP is syntax to appear more Java like. That was back when it looked like there was going to be a real Java hegemony in business programming. At the time I thought it was a slightly odd but defensible idea. Today I see that decision as an indicator of weak conceptually integrity. I think any system willing to give up its character so completely must lack, almost by definition, the conceptual integrity needed to be great.
I covered several concrete issues with PHP in Early impressions of PHP. All of those issues still stand but my biggest problem with PHP, after working with it for a while, is that is seems designed to actively discourage meta-programming. This means I find myself writing annoying amounts of boiler plate code2. I strongly believe that the future of programming is language-oriented. This make PHP hard for me because even rudimentary language oriented techniques are simply not feasible in PHP.
A Somewhat more minor annoyance is the lack of closures and blocks. I first learned blocks and closures about two years ago and now find programming without them mildly painful. I think that Mark Jason Dominus got it right when he said
in another thirty years people will laugh at anyone who tries to invent a language without closures, just as they’ll laugh now at anyone who tries to invent a language without recursion.
There are just so many common classes of problem that are simply and cleanly solved by closures that not having them seems like a crime. I hope it does not take thirty years, though.
It would not be fair to leave this post without a discussion of the good things about PHP. PHP excels at lowering the barrier to entry. There is no other system I am aware of that even come close the ease of getting start with PHP. The weakness of PHP’s conceptual integrity does not seem to noticeably impact productivity in the context of small systems. The idea that you can have a web application by creating one text file and copying it to the web server is radically powerful.
And then there is Smarty. Smarty is a really nice external DSL for generating web pages, i.e. a template engine. The core of Smarty is well thought out and has very nice extension mechanisms. I is a joy to work with. If you are doing PHP work I can strongly recommend Smarty.
As always, I need to point out that I am speaking primarily about PHP 4. I suspect that PHP 5 suffers from many of these issues but I have spent very little time in PHP 5.
Usually this boiler plate code gets written after I have already spent an inordinate amount of time tyring and failing to automate it. The usable area in PHP seems remarkably small. That means it is going to take a bit more running into the edges before I completely accept that they are really that close.