Using __autoload()

[jdc44]

Greetings
I know of the autoload() function and what it does, but I'm not sure how it is used. What I mean is, how does autoload() know about my classes? Does it "magically" know where my classes are and how many I have? Or, must I write a script that lists all my classes and their paths and call the autoload() function from that?

Thanks for any clarifications.
jdc44

[laserlight]

jdc44 wrote:

What I mean is, how does autoload() know about my classes?

The class name is passed as the argument to the autoload() function.

jdc44 wrote:

Does it "magically" know where my classes are and how many I have?

No. Recall that it is only invoked if a class whose definition is not yet available is used.

jdc44 wrote:

Or, must I write a script that lists all my classes and their paths and call the autoload() function from that?

The PHP manual's documentation of __autoload() has a simple example of how to do this without exhaustively listing each file.

[NogDog]

It does require some forethought and organization: you cannot get autoload() to work (at least not very easily) if the classes you want it to load are scattered willy-nilly around your file system and with no sort of naming convention that can be used to identify where they are. But if you do have a scheme, it can be fairly easy. Suppose you have the following class directory/file hierarchy:

www
|
+--classes
   |
   +--control
   |   |
   |   +--foo.php  [class name: Control_Foo]
   |   |
   |   +--bar.php  [class name: Control_Bar]
   |
   +--model
      |
      +--this.php  [class name: Model_This]
      |
      +--that.php  [class name: Model_That]

Then your __autoload() might be:

function __autoload($className)
{
   $path = strtolower(str_replace('_', '/', $className)) . '.php';
   require_once($_SERVER['DOCUMENT_ROOT'] . '/classes/' . $path);
}