Welcome to the first edition of the PHP performance series, a new series that I will be explaining ways to gain efficiencies and squeezing more performance out of your applications. This first edition, caching techniques, focuses on ways to cache data to optimize your current sites. Some of the concepts here are fairly easy to implement while others may take strategic design in the architecture of your application. Whether you are working on a high profile web application or simply a web development farm these concepts apply to the masses.
Opcode Caching
Opcode caching is likely one of the most simple and effective ways of increasing performance in PHP. By utilizing an Opcode cache you will eliminate many unneeded inefficiencies that happen during the execution process. Opcode caches solve this by storing the opcodes in memory in order to not compile files on each step in the process.
There are many opcode caches available for consumption. You have APC, XCache, eAccelerator and Zend Platform. You make your choice up of what you like the best as they all have advantages and disadvantages which is out of the scope of this article.
File Priming
This is typically more relevant to larger scale companies that have release processes. When you are pushing out a new release, typically you do not want to have your caching system waiting until each page is hit until it is processed in the opcode cache. Instead what can be done, is to run a utility script after the release is pushed out to run each file through the opcode caching extensions compile function. There is an example of this on my performance overview post which has a section about file priming for APC Each of the different opcode caches typically have a way to prime the files, so just look into the API documents.
Caching Variables
Many opcode caches also allow for you to place variable data, also known as user land data, into the cache (typically in memory). This is useful for storing your configuration values or data that is expensive to get and will likely not change.
Example: APC Variables
if (!$config = apc_fetch('config')) {
require('/path/to/includes/config.php');
apc_store('config', $config);
}A practical example of this was using the Zend Framework and simply running an ab bench after storing the results of the XML configuration file in the cache. This saved parsing time as well as extremely quick access to the configuration file.
Figure: APC Variables in Use
The Code
if (!$conf = apc_fetch('pbs_config')) {
$conf = new Zend_Config_Xml(PB_PATH_CONF . '/base.xml', 'production');
apc_store('pbs_config', $conf);
}The Benchmark Command
ab -t30 -c5 http://www.example.com/
Truncated by Planet PHP, read more at the original (another 22515 bytes)
