On Zend Framework lists there was a topic raised about performance impact of Zend_Loader component, which is used for - no surprise here! - loading classes, including autoloading, etc. Some folks thought that since Zend_Loader is executing some code before actual loading the required file, it must cost something. And it makes sense. However, how much does it cost?

He uses a set of scripts he developed to compare the bytecode caches of the requests both with and without the caching turned on. He ran the tests on a PHP 5.2 and PHP 5.3 installs with the lower (better) numbers coming from the latter in requests per second. He highly recommends turning this caching on on your system if you haven't already.

Here's the list:

• PHP Accelerators : APC vs Zend vs XCache with Zend Framework - a comparison of three tools - APC, the Zend Framework components and the XCache tool
• Zend Framework Performance Zend_Loader - a specific look at benchmarks on the Zend_Loader component
• PHP Accelerators: The Missing Details - benchmark results (and code) showing results from testing on the Zend_Loader component
• Accelerators Revisited - a revisit to some of the benchmarks made previously (to change things based on user contributed comments)

When you use Zend_Loader your files are wrapped in conditional statements. These statements prevent APC and all other cache/accelerator programs to have problems properly caching your file. [...] Now here is the catch-22. Depending on the size of your application and how often different classes are used you can run into problems.

His result doesn't have much to do with the component, though - he points out that conditionals of any type can slow things down in an application and that "benchmarking is your friend".

When Stefan asked me to write about the Zend Framework, I decided I would avoid copy-able code, simply because it doesn't re-enforce good software design. [...] The following is a brief summary of 4 components in the Zend Framework: Zend_Loader, Zend_Log, Zend_Config and Zend_Registry.

For each of the four components, he looks at how they can be used (reason why), some good and bad things about them and he includes some pseudocode to show the format for its use.