PHP is extremely quick. In fact, for many applications, both simple and complex, PHP can beat the likes of Java, ASP, ColdFusion, and ASP.NET with very little work.
Sometimes, however, the need for speed will be of fundamental importance to the overall success of your project. At these times, gaining that last drop of performance can mean the difference between success and failure, so planning your application with speed in mind is vital from the outset.
But there are other reasons for using PHP. For example, you may have inherited a poorly written application from another party and need to increase performance without spending money on new hardware. Although it's rarely pleasant working with other people's code, especially those who have not been lucky enough to read this book, you'd be surprised how easy it is to squeeze seconds off.
In this appendix, you'll learn to identify the different types of performance bottleneck and how to track down their culprits. Then, you'll look at how to design and code for optimum efficiency and speed, as well as how to retroactively repair bad code you've been unfortunate enough to inherit.