eAccelerator is a free open-source PHP accelerator, optimizer, and dynamic content cache. It increases the performance of PHP scripts by caching them in their compiled state, so that the overhead of compiling is almost completely eliminated. It also optimizes scripts to speed up their execution. eAccelerator typically reduces server load and increases the speed of your PHP code by 1-10 times.

You can find on Andrew’s side pages the php eaccelerator package for Debian Etch. Following this link brings you to his repository.

add deb http://debian.mcmillan.net.nz/debian etch awm
to your bin section of /etc/apt/sources.list

The following commands are needed to add Andrew’s key to your aptitude:
Debian:~# gpg –keyserver subkeys.pgp.net –recv-keys 0x8f068012;
Debian:~# gpg –export –armor 0x8f068012 | apt-key add -
Debian:~# aptitude update
Debian:~# aptitude install php5-eaccelerator

You have to edit your /etc/php5/apache2/php.ini and add the following lines at the end:
[eAccelerator]
extension=”eaccelerator.so”
eaccelerator.shm_size=”32″
eaccelerator.cache_dir=”/tmp”
eaccelerator.enable=”1″
eaccelerator.optimizer=”1″
eaccelerator.check_mtime=”1″
eaccelerator.debug=”0″
eaccelerator.filter=”"
eaccelerator.shm_max=”0″
eaccelerator.shm_ttl=”0″
eaccelerator.shm_prune_period=”0″
eaccelerator.shm_only=”0″
eaccelerator.compress=”1″
eaccelerator.compress_level=”9″

Finally just restart your Apache2 server for the changes to take effect.
Debian:~# /etc/init.d/apache2/ force-reload