note 78122 added to function.spl-autoload-register

The spl_autoload_register() method registers functions in
its stack in the order that spl_autoload_register() was
called, and subsequently if you want an autoload function to
override previous autoload functions you will either need to
unregister the previous ones or change the order of the
autoload stack.

For example, say in your default implementation of an
autoload function you throw an exception if the class cannot
be found, or perhaps a fatal error.  Later on in your code
you add a second implementation of an autoload function
which will load a library that the previous method would
fail on.  This will not call the second autoloader method
first, but rather will continue to error out on the first
method.

As previously mentioned, you can unregister the existing
autoloader that errors out, or you can create a mechanism
for unregistering and re-registering the autoloaders in the
order you want.

Here is a sample/example of how you might consider
re-registering autoloaders so that the newest autoloader is
called first, and the oldest last:

<?php

function spl_autoload_preregister( $autoload ) {
	// No functions currently in the stack.
	if ( ($funcs = spl_autoload_functions()) === false ) {
		spl_autoload_register($func);
	} else {
		// Unregister existing autoloaders...
		foreach ($funcs as $func) {
			spl_autoload_unregister($func);
		}
		
		// Register the new one, thus putting it at the front of
the stack...
		spl_autoload_register($autoload);
		
		// Now, go back and re-register all of our old ones.
		foreach ($funcs as $func) {
			spl_autoload_register($func);
		}
	}
}

?>

Note: I have not tested this for overhead, so I am not 100%
sure what the performance implication of the above example
are.
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