Zend, the primary developers of PHP, offers another pair of products that together can help improve performance:

• Zend Encoder, a product that encodes your PHP scripts to protect your PHP scripts against reverse engineering.
• Zend Optimizer, a product that works with the files generated by the Zend Encoder and applies multi-pass optimizations to help speed up the execution of your PHP code.

If your application is not currently running under a platform supported by the Zend Encoder and Zend Optimizer, consider moving to a platform supported by these products. While the Zend Optimizer is free, the Zend Encoder is not. You will also need to weigh the cost of this product against the benefits achieved when using it in conjunction with the Zend Optimizer.