PHP accelerator

A PHP accelerator is an extension designed to boost the performance of software applications written using the PHP programming language. Most PHP accelerators work by caching the compiled bytecode of PHP scripts to avoid the overhead of parsing and compiling source code on each request (some or all of which may never even be executed). For best performance, caching is to shared memory with direct execution from the shared memory and the minimum of memory copying at runtime. A PHP accelerator typically reduces server load and increases the speed of PHP code anywhere from 2-10 times, depending on factors such as the inherent execution time of the PHP application and the percentage of source code actually executed on a given request. While a code optimizer may even slow down overall performance when used in isolation, it can provide an additional performance boost when coupled with a code cache as the optimization effort is performed just once.

List of PHP accelerators

Alternative PHP Cache

Alternative PHP Cache (APC) is a free, open source framework that optimizes PHP intermediate code and caches data and compiled code from the PHP bytecode compiler in shared memory.
* Home page: http://pecl.php.net/package/APC
* PHP version: works with all PHP versions including PHP5.2
* Latest stable version: 3.0.19 (2008-05-15)
* Status: stable, actively maintained. Will be included in the core of PHP 6.
* Download link: http://pecl.php.net/package/APC (*nix)
* Download link for Windows: http://pecl4win.php.net/ext.php/php_apc.dll (oldest, buggy, 3.0.16), and in latest compiled pecl snaphot - http://snaps.php.net/
* Official installation help: inside the source

eAccelerator

eAccelerator was born in December 2004 as a fork of the Turck MMCache project. Turck MMCache was created by Dmitry Stogov and much of the eAccelerator code is still based on his work. eAccelerator also contained a PHP encoder and loader, but the development staff discontinued the encoder and removed this feature after December 2006.
* Home Page: http://eaccelerator.net/
* PHP version: Supports PHP 4 and all PHP 5 releases including 5.2. In older releases, the encoder will only work with PHP versions from the 4.x.x branch. eAccelerator will not work with any other versions of PHP.
* Latest stable version: 0.9.5.3 (2008-05-18)
* Status: Actively maintained
* Download link: http://bart.eaccelerator.net/source/0.9.5/
* Official installation help: http://eaccelerator.net/wiki/InstallFromSource

XCache

XCache is a fast, stable PHP opcode cacher that has been tested and is now running on production servers under high load. It is tested on linux. ThreadSafe/Windows is also supported. It is designed to overcome a lot of problems that have been seen with other competing opcachers, such as being able to be used with new PHP versions. New kid on the block developed by mOo who is also one of developers of Lighttpd. Developed to overcome some of the limitations of the existing solutions at that time.
* Home Page: http://xcache.lighttpd.net/
* PHP version: PHP_5_1 PHP_5_2 PHP_5_3 HEAD(6.x)
* Latest stable version: Latest stable version: 1.2.2 (Released on 2007-12-29)
* Status: Actively maintained (different releases stable/unstable/devel)
* Download link: http://xcache.lighttpd.net/pub/Releases/1.2.2/xcache-1.2.2.tar.gz
* Official installation help: http://trac.lighttpd.net/xcache/wiki/InstallFromSource

Zend Optimizer

Zend Optimizer is a closed source solution. Zend Optimizer it is not an accelerator in the same sense as other entries discussed here as it does not contain code caching. It does contain a code optimizer that will generally speed execution in some cases. While heavily execution bound scripts may show a measurable speed increase, real world applications may not show any significant performance improvement as the time taken optimizing scripts may exceed the performance gains. It is useful primarily to run scripts protected by Zend Guard.
* Home Page: http://www.zend.com/products/guard/optimizer/

Zend Platform

Zend Platform (formerly Zend Cache and then Zend Accelerator) is a commercial Web Application Server product. It has a complete set of performance capabilities that includes more than a simple PHP accelerator. Features include code caching/acceleration, data caching, content (html output) caching, download optimization and off-line (asynchronous) processing capabilities that can result in significant performance improvements for most PHP applications. It also includes detailed PHP monitoring and root cause analysis support to help in tuning and debugging, session fail-over support for HA (High Availability) needs and other integration capabilities including Java integration.
* Home Page: http://www.zend.com/products/platform

ionCube PHP Accelerator

Launched in 2001, ionCube PHP Accelerator (PHPA) was the first freely available PHP performance solution to match the performance of the commercial Zend Cache product and maximize the performance potential of PHP. Created before ionCube Ltd. was founded and at a time when the performance of PHP was regarded as lackluster when compared to other popular web programming languages, PHPA made accelerated PHP available to almost everyone and showed that PHP need not be the laggard in the performance stakes. In response to early concerns raised by Zeev Suraski of Zend Technologies about the effect that an open source rival might have on their commercial alternative, the author of PHPA chose to keep the project closed source. Although closed source, the availability of PHPA on a wide variety of platforms led to its extensive adoption world wide from small sites to Yahoo!. It also inspired the redevelopment of APC to use the shared memory execution techniques that PHPA and Zend Cache had adopted instead of deserialization on each request that incurred performance penalties. Other accelerators such as mmcache subsequently appeared in later years. PHPA is now discontinued and the development of a more advanced replacement has been announced.
* Home Page: http://www.php-accelerator.co.uk / http://www.ioncube.com

Turck MMCache

Turck MMCache is now discontinued, although it is still widely used.
* Home Page: http://turck-mmcache.sourceforge.net/index_old.html

External links

* [http://2bits.com/articles/benchmarking-drupal-with-php-op-code-caches-apc-eaccelerator-and-xcache-compared.html Benchmarking Drupal with PHP op-code caches: APC, eAccelerator and XCache (and Standard PHP) compared] from April 2008.
* [http://itst.net/654-php-on-fire-three-opcode-caches-compared PHP on Fire: Five Opcode Caches compared] including a [http://itst.net/wp-content/uploads/2006/10/PHP%20Bytecode%20Cacher%20Review.html complete chart] featuring Zend Platform, APC, XCache, eAccelerator ionCube Encoder and Standard PHP benchmarks. Made in October 2006.