A few other major features will be part of PHP 5, but luckily nothing that renders moot the information you've learned so far in this book! The next few sections provide a glimpse at these features.
PHP 5 will contain an embedded database engine, called
SQLite . This is not at all meant to replace a robust database like MySQL, PostgreSQL, or Oracle. Instead, this simple, speedy little database can store database in both files and memory and thus would be good for something like storing session data and application configuration informationsimple INSERTs and SELECTs. While there is not much information currently available regarding the inner workings of this database engine, based on the initial indications of speed it is definitely something to keep an eye on, for uses like those indicated earlier.
PHP 4 uses several different third-party libraries to control XML parsing and rendering: Expat, libxml, and Sablotron. Expat is currently relied upon more heavily by developers and is pretty stable, but developers use the other two as well. The point is, PHP 4 has no single stable and reliable XML rendering and parsing mechanism.
With PHP 5, the development group has settled upon one XML library, Gnome's libxml, as the foundation for the DOM extension. This library has been determined to be very fast and full-featured, and thus a good foundation on which to rebuild the XML functionality in PHP.