1. download the source code and upload it to your server
2. execute
export PHP_PREFIX="/usr/local/php/"
where /usr/local/php/ is my path to where php is installed
3. $PHP_PREFIX/bin/phpize
4. ./configure --enable-eaccelerator=shared --with-php-config=$PHP_PREFIX/bin/php-config
5. make
6. make install
7. now go to php.ini and include this code:
zend_extension="/usr/local/php5.2.12-fcgi/lib/php/extensions/no-debug-non-zts-20060613/eaccelerator.so"
eaccelerator.shm_size="128"
eaccelerator.cache_dir="/tmp/eacc-php5.2.12-fcgi"
eaccelerator.enable="1"
eaccelerator.optimizer="1"
eaccelerator.check_mtime="1"
eaccelerator.debug="0"
eaccelerator.filter="*.php"
eaccelerator.shm_max="0"
eaccelerator.shm_ttl="7200"
eaccelerator.shm_prune_period="7200"
eaccelerator.shm_only="0"
eaccelerator.compress="1"
eaccelerator.compress_level="8"
eaccelerator.keys = "shm"
eaccelerator.sessions = "shm"
eaccelerator.content = "shm"
make sure you change the extension path above to fit your php extension directory
8. restart apache