While there are many books on learning PHP and developing small applications with it, there is a lack of information on "scaling" PHP for large-scale, business-critical systems. PHP is now starting to make inroads into large-scale business-critical Web systems. The introduction of PHP 5 two years ago brought enterprise-grade capabilities to PHP -- capabilities that have been expanded upon and solidified with the subsequent release of PHP 5.1. Schlossnagle's Advanced PHP Programming demonstrates that PHP is ready for enterprise Web applications by showing the reader how to develop PHP-based applications for maximum performance, stability, and extensibility.