Core PHP Programming, Third Edition

6.12. Class Autoloading

When you attempt to use a class you haven't defined, PHP generates a fatal error, of course. The obvious solution to this situation involves adding a class definition, probably by issuing an include statement. After all, you should know which classes a script uses. However, PHP offers class autoloading, which may save programming time. When you attempt to use a class PHP does not recognize, it looks for a global function named __autoload. If it exists, PHP calls it with a single parameter, the name of the class. Inside the function, you may take the necessary steps to create the class.

Listing 6.15 demonstrates the use of __autoload. It uses a simple scheme that assumes files in the current directory match each class. ...