This works for php4 and php5, apache1.3 and 2!
first get php5-dev (or php4-dev, depending on what you use) apt-get install php5-dev
get eaccelerator from here and unpack it.
cd eaccelerator-0.9.5
phpize
./configure
make
make install
create the eaccelerator cache directories
mkdir /tmp/eaccelerator
chmod 0777 /tmp/eaccelerator
and add this to your php.ini (in my case: /etc/php5/apache2/php.ini )
extension=eaccelerator.so
eaccelerator.shm_size=64
eaccelerator.cache_dir=/tmp/eaccelerator
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
eaccelerator.allowed\_admin\_path=/path/to/control.php
adjust the memory to whatever you like. Copy the control.php to whatever path you like (must be some htdocs accessible path) and set the path in eaccelerator.allowed_admin_path= … edit the file and user/password. now restart apache and you are done! go to the link where control.php is and check if you can login and if it works.