This are the steps I took on my CentOS Box.
The provided instructions are for 32-bit CentOS
eAccelerator Installation:
Time required: 1 minute
1. If using PHP v5+, download the lastest compatible version and extract. Remember v0.9.5.3 is the last version that supports user objects, later versions only support opcode caching.
# cd /usr/local/src
# wget http://bart.eaccelerator.net/source/0.9.5.3/eaccelerator-0.9.5.3.tar.bz2
# tar -xjf eaccelerator-0.9.5.3.tar.bz2
# cd eaccelerator-0.9.5.3
2. Note the path returned for the following command:
# whereis php-config
3. Use the output from #2 to modify the --with-php-config flag in the following compile command:
# phpize
# ./configure --with-eaccelerator-shared-memory --with-php-config=/usr/bin/php-config
# make
# make install
The result should be similar to:
Installing shared extensions: /usr/lib/php/modules/
4. You can also use the eaccelerator.ini file we prepared for you:
# cp /var/www/vhosts/domain.com/httpdocs/wp-content/plugins/w3-total-cache/ini/eaccelerator.ini /etc/php.d/
5. Restart apache when ready:
# /etc/init.d/httpd restart
6. You're done! eAccelerator should now be available. If the following command retuns anything, you're all set:
# php -r 'phpinfo();' | grep 'eaccelerator'