Book excerpt: While many architects use PHP for projects, they are often not aware of the power of PHP in creating enterprise-level applications. This book covers the latest version of PHP – version 5 -- and focuses on its capabilities within a multi-tier application framework. It contains numerous coding samples and commentaries on them. A chapter discusses object orientation in PHP as it applies to the multi-tier architecture and other chapters discuss HTTP and SOAP, the two communication protocols most useful in tying together multiple layers. There is also coverage of database design and query construction as well as information about tricks you can use in generating user interfaces. - Covers PHP as it relates to developing software in a multi-tier environment—a crucial aspect of developing robust software with low cost and ease of use as design goals. - Makes extensive use of Simple Object Access Protocol (SOAP) and Web Services as implemented in PHP and NuSOAP. - Shows precisely how to make use of the InnoDB table type newly available in MySQL. InnoDB supports true referential integrity and row-level locking. - An application example (a multi-currency bookkeeping application) runs throughout the book, showing various PHP capabilities as well as the database interaction.