Apache (the http server) is one of the major reasons why PHP is so popular; but with today’s trend of using front-controllers have we obsoleted our old friend?
In the olden days we used to write web scripts in Perl and Apache would have to fork a new interpreter process to execute each script request. This was really slow, especialy on the hardware available at the time. PHP came along and provided an embedded interpreter (mod_php) and gave a huge performance boost to the web-scripting world. This was a major motivator for migrating from Perl to PHP. It doesn’t hurt that Apache also happens to be a solid piece of software that can be (and probably has been) be compiled on pretty much all operating systems out there. PHP has unashamedly piggy-backed on its host’s popularity, and for that, we salute you Apache!
Another reason PHP gained popularity is that you could drop a PHP file into any directory and Apache would just run it - no need for the “cgi-bin”. Today, website best-practice would typically recommend against executing “physical .php files” like add-user.php, and instead have pretty urls like /users/add (good for readability and for SEO). Apache provides us with such functionality though a variety of methods, the most popular being mod_rewrite. We can easily use rewrite rules to route /users/add => add-user.php. Thing is, we’re not happy with that. We’ve all got drunk on “MVC” and cool applications use front-controllers (a single entry point for all requests, normally “index.php”). So instead of using Apache’s built-in functionality, we’re re-implementing the wheel inside our own applications. Why use mod_rewrite when we can do the same thing, but slower, using Zend_Controller_Router_Route_Regex? /me rolls-eyes.
We’re even ditching Apache for static stuff too. If you don’t already, it’s probably only a matter of time before you run CSS and Javascript request through PHP too (for good reason). Yahoo’s frontend performance guidelines suggest reducing the number of HTTP requests is important, so it makes sense to generate (and cache) a single CSS file and a single JS file. You might also do clever stuff like postfixing the urls with a version number to help caching, and/or gzip/minify/manipulate headers. These are good things to do, but you’re now using Apache even less.
So what is left? Images, video, flash? Lots of sites which graduate beyond a single-server use a “static file server” to handle this stuff. There’s also no point using a feature-rich, but slower, server like Apache for doing basic static file serving, when alternatives like Lighty/nginx can do this more efficiently. Another option might be to locate static content on a NAS of some sort which Apache will alias (Alias /images /mnt/nas/images). We’ve now got a document root that looks like this:-
index.php
.htaccess (to route everything to index.php)
Wow, clean! (Our PHP code is outside the docroot in some include_path location). I just had a thought - we could get rid of the document root entirely, but sticking this in our virtualhost: “php_value auto_prepend_file /path/to/app/index.php”. (That would be pretty funny, running a site without a docroot).
We don’t really use Apache for much, so why do we use it at all? I think it boils down to being a nice host environment for PHP. There’s nothing really wrong with that, except PHP is tightly coupled to Apache. I think Apache rocks, but if we just end up using it as a host for PHP, then that’s bloated overkill? What about if we stripped out the features of Apache that we dont use until we’ve got a lightweight http wrapper for our PHP app to run in… isn’t that what Rubyists do with Mongrel?
The type of code I write in PHP today is request/response stuff. I get an incoming HTTP request, do some processing, and create an HTTP response. That sounds obvious, but the subtle difference to what I was doing 5 years ago, is that my PHP code is taking care of ALL of the request lifecycle. I don’t use Apache for authentication, logging, uri-routing, headers setting, gzip, caching etc - everything is done by my code. It’s this slight shift in paradigm that makes me think “scripting application servers” like Mongrel+Rails or CherryPy are worth keeping an eye on, and another reason why I question the future of PHP.