Zend Optimizer is a free application that runs files encoded by Zend Encoder, enhancing the running speed of PHP applications. This free application uses multi-pass code optimizations to speed up PHP applications. The increase in speed reduces CPU load for the server typically cutting latency time in by 20-50%.

1. To start the installation, you have to download Zend Optimizer. You can do that from the site www.zend.com/store/free_download.php?pid=13
2. If you have an account with Zend, you just login; if you don't, you have to sign up to get access for a free download. Press sign up and follow the instruction. After submitinig your form, you will be taken directly to Zend Optimizer downloads.
3. You choose your Operational System and PHP version 4.1.0 or later. The distribution will start to download.
4. Login to your web box where Zend Optimizer has to be installed.
5. For Zend installation, you must have the file php.ini in the directory /user/local/lib/. Since the distribution doesn't include this file, you have to copy php.ini to the directory specified above.
6. Go to the directory where your Zend distribution lies and extract it using the following command:
   tar xzf zend*****.tar.gz - the asterisks stand for any characters
   After executing this command, Zend Optimizer directory will be created. The exact name of this directory depends on the Zend version and system characters.
7. To proceed with the installation, enter the following commands:
   cd Zendoptimizer*** (the asterisks stand for any characters) - move to the directory where your Zend lies
   ./install-tty.sh - start Zend installation
8. Read the license carefully. If you agree, enter yes, otherwise enter no. You will be asked to choose how you want to install Zend. For the default installation, simply press Enter. As the password for the Zend Product User Interface, enter a compbination of at least 4 characters, then confirm it. Follow the further instructions.
9. You must restart Apache.
   Linux users have to do that with the command /etc/rc.d/init.d/httpd restart
   For FreeBSD, use /usr/local/etc/rc.d/apache.sh.stop
   /usr/local/etc/rc.d/apache.sh.start
10. If apache crashes with a segmentation fault error, the most probable reason is that the file usr/local/lib/php.ini was created incorrectly. Open it with a text editor and remove all lines except the first five so php.ini file looks as follows:
    zend_gui_password=your_encoded_zend_gui_password
    [PHP]
    zend_extension=/usr/local/Zend/lib/ZendOptimizer.so
    zend_optimizer.optimization_level=15
11. Check if Zend was succefully installed by putting a php file with the following content to any directory of your site
    <? phpinfo() ?>
    Then open this file in a browser. Zend Optimizer sections must appear. If your Zend Optimizer was installed successfully, the following items will be enabled :

    Optimization Pass 1	Enabled
    Optimization Pass 2	Enabled
    Optimization Pass 3	Enabled
    Zend Loader	Enabled

12. If one of the given items was not enabled, contact Zend Optimizer support.