A few other major features are 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 contains an embedded database engine, called SQLite. This is not at all meant to replace a robust database system like MySQL, PostgreSQL, or Oracle. Instead, this simple, speedy little database can store records in both files and memory, and thus would be good for something like storing session data and application configuration informationsimple INSERTs and SELECTs.
To use SQLite, you must have a fundamental understanding of how databases, tables, and fields all work together, and SQL syntax itself. Virtually anything you want do with MySQL, you could do (with a little elbow grease in some instances) with SQLite. Everything you have learned in this book is still usable with regard to the process of connecting to a database, issuing queries and obtaining resultsexcept that you learned to use the MySQL-specific functions for sending the commands to the MySQL server. SQLite has its own set of functions that you use, to perform the same types of tasks.
For detailed information on the database and its accompanying PHP functions, please visit the SQLite Web site at http://www.sqlite.org/ and the PHP manual section for SQLite at http://www.php.net/sqlite/.
By the Way
SQLite is installed by default during the installation of PHP 5.
PHP 4 uses several different third-party libraries to control XML parsing and rendering: Expat, libxml, and Sablotron are examples. 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, all XML-related functions were rewritten to use Gnome's libxml2. 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. Now, PHP developers who use SAX, DOM, XSLT, SOAP and the new SimpleXML extension will all use libxml2-based functionality.