PHP performance considerations?

Question

I'm building a PHP site, but for now the only PHP I'm using is a half-dozen or so includes on certain pages. (I will probably use some database queries eventually.)

Are simple include() statements a concern for speed or scaling, as opposed to static HTML? What kinds of things tend to cause a site to bog down?

Answer 1

Strictly speaking, straight HTML will always serve faster than a server-side approach since the server doesn't have to do any interpretation of the code.

To answer the bigger question, there are a number of things that will cause your site to bog down; there's just no specific threshold for when your code is causing the problem vs. PHP. (keep in mind that many of Yahoo's sites are PHP-driven, so don't think that PHP can't scale).

One thing I've noticed is that the PHP-driven sites that are the slowest are the ones that include more than is necessary to display a specific page. OSCommerce (oscommerce.com) is one of the most popular PHP-driven shopping carts. It has a bad habit, however, of including all of their core functionality (just in case it's needed) on every single page. So even if you don't need to display an 'info box', the function is loaded. On the other hand, there are many PHP frameworks out there (such as CakePHP, Symfony, and CodeIgniter) that take a 'load it as you need it' approach.

I would advise the following:

1. Don't include more functionality than you need for a specific page
2. Keep base functions separate (use an MVC approach when possible)
3. Use require_once instead of include if you think you'll have nested includes (e.g. page A includes file B which includes file C). This will avoid including the same file more than once. It will also stop the process if a file can't be found; thus helping your troubleshooting process ;)
4. Cache static pages as HTML if possible - to avoid having to reparse when things don't change

Answer 2

Certainly include() is slower than static pages. However, with modern systems you're not likely to see this as a bottleneck for a long time - if ever. The benefits of using includes to keep common parts of your site up to date outweigh the tiny performance hit, in my opinion (having different navigation on one page because you forgot to update it leads to a bad user experience, and thus bad feelings about your site/company/whatever).

Using caching will really not help either - caching code is going to be slower than just an include(). The only time caching will benefit you is if you're doing computationally-intensive calculations (very rare, on web pages), or grabbing data from a database.

Answer 3

Sounds like you are participating in a bit of premature optimization. If the application is not built, while performance concerns are good to be aware of, your primary concern should be getting the app written.

Includes are a fact of life. Don't worry about number, worry about keeping your code well organized (PEAR folder structure is a lovely thing, if you don't know what I'm talking about look at the structure of the Zend Framework class files).

Focus on getting the application written with a reasonable amount of abstraction. Group all of your DB calls into a class (or classes) so that you minimize code duplication (KISS principles and all) and when it comes time to refactor and optimize your queries they are centrally located. Also get started on some unit testing to prevent regression.

Once the application is up and running, don't ask us what is faster or better since it depends on each application what your bottleneck will be. It may turn out that even though you have lots of includes, your loops are eating up your time, or whatever. Use XDebug and profile your code once its up and running. Look for the segments of code that are eating up a disproportionate amount of time then refactor. If you focus too much now on the performance hit between include and include_once you'll end up chasing a ghost when those curl requests running in sync are eating your breakfast.

Though in the mean time, the best suggestions are look through the php.net manual and make sure if there's a built in function doing something you are trying to do, use it! PHP's C-based extensions will always be faster than any PHP code that you could write, and you'll be surprised how much of what you are trying to do is done already.

But again, I cannot stress this enough, premature optimization is BAD!!! Just get your application up off the ground with good levels of abstraction, profile it, then fix what actually is eating up your time rather than fixing what you think might eat up your time.

Answer 4

Nah includes are fine, nothing to worry about there.

You might want to think about tweaking your caching headers a bit at some point, but unless you're getting significant hits it should be no problem. Assuming this is all static data, you could even consider converting the whole site to static HTML (easiest way: write a script that grabs every page via the webserver and dumps it out in a matching dir structure)

Most web applications are limited by the speed of their database (or whatever their external storage is, but 9/10 times that'll be a database), the application code is rarely cause for concern, and it doesn't sound like you're doing anything you need to worry about yet.

Answer 5

Before you make any long-lasting decisions about how to structure the code for your site, I would recommend that you do some reading on the Model-View-Controller design pattern. While there are others this one appears to be gaining a great deal of ground in web development circles and certainly will be around for a while. You might want to take a look at some of the other design patterns suggested by Martin Fowler in his Patterns of Enterprise Application Architecture before making any final decisions about what sort of design will best fit your needs.

Depending on the size and scope of your project, you may want to go with a ready-made framework for PHP like Zend Framework or PHP On Trax or you may decide to build your own solution.

Specifically regarding the rendering of HTML content I would strongly recommend that you use some form of templating in order to keep your business logic separate from your display logic. I've found that this one simple rule in my development has saved me hours of work when one or the other needed to be changed. I've used http://www.smarty.net/">Smarty and I know that most of the frameworks out there either have a template system of their own or provide a plug-in architecture that allows you to use your own preferred method. As you look at possible solutions, I would recommend that you look for one that is capable of creating cached versions.

Lastly, if you're concerned about speed on the back-end then I would highly recommend that you look at ways to minimize your calls your back-end data store (whether it be a database or just system files). Try to avoid loading and rendering too much content (say a large report stored in a table that contains hundreds of records) all at once. If possible look for ways to make the user interface load smaller bits of data at a time. And if you're specifically concerned about the actual load time of your html content and its CSS, Javascript or other dependencies I would recommend that you review these suggestions from the guys at Yahoo!.

Answer 6

To add on what JayTee mentioned - loading functionality when you need it. If you're not using any of the frameworks that do this automatically, you might want to look into the __autoload() functionality that was introduced in PHP5 - basically, your own logic can be invoked when you instantiate a particular class if it's not already loaded. This gives you a chance to include() a file that defines that class on-demand.

Answer 7

The biggest thing you can do to speed up your application is to use an Opcode cache, like APC. There's an excellent list and description available on Wikipedia.

As far as simple includes are concerned, be careful not to include too many files on each request as the disk I/O can cause your application not to scale well. A few dozen includes should be fine, but it's generally a good idea to package your most commonly included files into a single script so you only have one include. The cost in memory of having a few classes here and there you don't need loaded will be better than the cost of disk I/O for including hundreds of smaller files.