Even in the older days of the web, application developers could not afford to be ignorant of SEO practices - but in today's world, it's a vital skillset for maintaining relevancy. One of the most neglected aspects of SEO is page load time, and the way your PHP code is written can make a huge difference in the speed your users (and the Google search spiders) experience. Obviously, one of the most effective things to do is ensure you use a high-quality hosting provider, but this isn't always an option. Fortunately a couple of simple tips and tricks in PHP can make a huge difference in load times, so lets take a quick look at the most popular methods.
One of the most useful things you can do, especially when you're writing extensive code segments, is to employ a simple PHP caching system. This is especially helpful when there isn't a heavy amount of reparsing required for each user navigation step, as it lets you skip the reparsing step. If, for example, the user is navigating through a large number of database entries, simply dump the output from your first parse into an html file, and display that to the user when they revisit the same page in the same session. This can dramatically reduce the load on your server from numerous database queries, and can make a huge difference in your user experience.
Next, take a good long look at the external requests your site is making. A growing trend among websites is to pull lots of data from different sources - Twitter feeds, news stories, popular blog comments, etc - but it's important to not let this tendency get ahead of us. This is especially true when you're working on code for a Wordpress or similar-style blog, as the ease of incorporating PHP widgets can make some developers cram far too many requests onto a single page, dramatically increasing load time.
If you're feeling adventurous, it's possible to use PHP to compress your CSS and other files, but we'll save that for another post - you should be able to see a large difference in your load times just from these simple tips.