php accelerator review
APC — standard choice, included in PECL, comes prepackaged in most Linux distros, to be bundled in by default in PHP6. As a bonus it can serve as data cache (something like local memcache).
eAccelerator was popular, for some time it was the fastest bytecode cache. But the difference in speed is not enough to justify choosing it over APC.
Turck MMcache — dead. eAccelerator was forked from it.
ionCube — dead.
APC is pretty much the standard choice. It's scheduled to be included in PHP 6 core. Unlike most of the other candidates, it's stable and it's free.
Here is a comparison of three of them, APC, Zend and XCache:
http://blog.digitalstruct.com/2007/12/23/php-accelerators-apc-vs-zend-vs-xcache-with-zend-framework/