PHP is not the fastest scripting language, that truly a fact. Except from optimizing the scripts there a few possibilities to speed everything up. One is to install a byte code optimizer and cache on your server. They cache the byte code created by the PHP parser and try to optimise it. So every time some one requests for a page on your server the script does not have to be parsed again. This brings a speedup of 120 – 250% depending on you script. There are several byte code caching program available, the one I like most is eAccelerator. Sadly eAccelerator is not available through the Ubuntu repositories so you have install them yourself. Here is a short description how to archive this!
Everything is done from the terminal as a root user.

• Prepare you system for compiling a PHP extension:

  apt-get install build-essential php5-dev

• Choosing a folder for build process. I used “/usr/local/src/”
• Getting the sources from the eAccelerator site:

  wget http://bart.eaccelerator.net/source/0.9.5.3/eaccelerator-0.9.5.3.zip

• Extract and delete the archive

  unzip eaccelerator-0.9.5.3.zip && rm eaccelerator-0.9.5.3.zip

• Enter the folder

  cd eaccelerator-0.9.5.3

• Prepare as a new PHP extension and compilation

  phpize
  ./configure --enable-eaccelerator=shared

• Compile and install

  make
  make install

  The install process prints out a folder where eAccelerator has been installed. Remember or copy it, you will need this later.

• Enabling eAcceletor: Editing your “php.ini” or create a new ini file in you conf.d directory of PHP. (You can find them here: “/etc/php5/”.) Insert the following:

  zend_extension                  = "/usr/lib/php5/20060613+lfs/eaccelerator.so"
  eaccelerator.shm_size           = "0"
  eaccelerator.cache_dir          = "/var/cache/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     = "7"
  eaccelerator.allowed_admin_path = "/var/www/eaccelerator"

  In the first line enter the path printed out during the install. In the last line you could enter a directory for the eAccelerator admin tool, if you want to use it.

• Create the cache directory:

  mkdir /var/cache/eaccelerator
  chown www-data.www-data /var/cache/eaccelerator

• Restart you Apache!

  /etc/init.d/apache2 restart

There are a lot of setting in the ini file. The whole list and the description of them could be found here:  Ini-settings.

To check if everything is working open up a page on the server that contains the “php_info();” command. There should be some thing like this:

eAccelerator

Enjoy the speed!