Ultimately, none of the techniques presented in this book would be practical if they didn’t provide a solid foundation on which to build large web applications that perform quickly and efficiently. This chapter shows how to use the foundation from the previous chapters to monitor and tweak the performance of your application.
You may well get a performance boost simply by following the practices already presented in this book. For example, the semantically meaningful HTML presented in Chapter 3 can speed up page display for several reasons. Likewise, modular techniques for large-scale PHP (see Chapter 7) generally create a faster site than jumping in and out of the PHP interpreter multiple times whenever needed.
But every professional web developer devotes time to performance as an end in itself, so this chapter shows how performance optimization interacts with the techniques in this book. To guide our discussion, we’ll explore some of the recommendations presented in High Performance Web Sites (O’Reilly). This book, based on research conducted by Steve Souders at Yahoo!, suggests that for most websites, backend performance accounts for only 10 to 20 percent of the overall time required for a page to load; the remaining 80 to 90 percent is spent downloading components for the user interface. By following a set of 14 rules, many web applications can be made 20 to 25 percent faster.
These statistics emphasize the importance of paying close attention to the performance ...