Since everyone else seems to have a list of how to speed up PHP Apps, I thought it was about time I made one. Here’s some basic rules for speeding up PHP Applications:

• Avoid including large files/classes. The more PHP has to process, the slower it is. A lot of frameworks have needlessly large classes. It’s recommended that you split things up into smaller “modules” and include them as needed. Also, only include what you need. PHP has to process everything, even the stuff you don’t use. With some sites, I’ve seen the number requests per second increase, 4 times, simply by moving away from needlessly large frameworks and unneeded includes.
• Use PHP’s built-in functions whenever you can. PHP has a lot of functions for working with strings, arrays, etc. A lot of times, they can save you headaches, and improve performance over user created functions.
• Avoid Regular Expressions. Instead, use functions like str_replace, in place of preg_replace, or strstr, in place of preg_match, when possible.
• Be careful of the way you reference objects. PHP is known to have trouble with garbage collection under certain situations, such as when you’re dealing with classes that are circular-referenced. These types of situations usually go unnoticed, until PHP start exceeding it’s memory limit.
• Avoid functions like file_get_contents(), and file_put_contents(), when working with large files… Unless you want to run out of memory.
• Use memcached, aggressively if possible. Hmm, lets see, 100 requests/second vs 1000 requests/second… On the same server. It’s a no brainer.
• Don’t ever use persistent connections. They may seem like a good idea, and they may appear to make your app faster in benchmarks, but it will severely cripple your ability to handle high traffic… Let me explain, persistent connections and connection pooling aren’t the same. Persistent connections are per user, and users will often end up with 2 or 3 persistent connections open for them. Nobody else can use these connections; this leads to your server running out of database connections with a relatively small number of users (think 40-60). If you really need this functionality, use an actual connection pooler.
• Avoid making your database grumpy; most bottlenecks are related to the database. This typically means avoiding sequential scans, aggregate functions, etc. With MySQL, avoid complex JOINs, as well as date range scans, and “WHERE column IN (SELECT …)” queries. With PostgreSQL, avoid “SELECT COUNT(*)”, and keep the total number of queries to a minimum.
• Get more servers. Single servers can only handle so many requests per second. When you get to a point where your server is struggling under the load, and there’s no clear bottlenecks, the only thing you can do is scale to your needs.

This entry was posted on Friday, July 4th, 2008 at 11:06 am and is filed under PHP. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.