Question

I’ve discovered the __autoload function today and after reading the official manual page of this function there’s a point I don’t get at all.

What’s clearly the difference between using __autoload() and let’s say require_once?

because it looks autoload is the new fashion way of doing the required includes but to me it’s far better to use require_once instead. Hence, __autoload has to be defined into all the php files which means writing its code down there, if I put ALL my includes/require_once/…etc into one file let’s call it main_header.php then all I’ll need to do in my web app files is write one line of code:

<?php require_once('main_header.php');  ?> 

Am I wrong somewhere?

Answer 1

I can see two things going for autoloading (not necessarily __autoload; prefer the more modern spl_autoload_register instead):

1. You don’t need to explicitly include the classes. Of course, you could make a main_header.php as in your example, but then the next item comes into effect.
2. You don’t have to load 100 classes if you are only going to use 10 of them.

It’s also worth to point out that autoloading is also triggered when unserializing an object of a class that has not been yet defined, which makes things infinitely more practical. Of course there is another hook in unserialize for this (the configuration setting unserialize_callback_func), so autoloading is not technically necessary. It’s definitely nicer though.