php __autoload（）函数，如何使用

Question

I just started learning PHP from a book. In the OOP chapter there is an explanation of the __autoload() function for "Automatically Load Class Files" but my book doesn't say where I should declare this function.

I tried to Google it and in the PHP documentation but I really can't find where I should declare this function. In "global scope" (I don't know if it is the same as JavaScript)? Inside the class that should be autoloaded? Or in the "local scope" of the class where I have to load the class?

Answer 1

The way of using the __autoload() function is :

<?php

    function __autoload($class){
        if(file_exists($class . ".php")){
            require_once $class . ".php";
        }
    }


    $class1 = new Class1();
    $class2 = new Class2();

On the very top of your page declare the function than you can start using it just like in the example below .

If you want it to be available site-wide than consider making a new file type the code there and include that file in the top of your page.

something.php

<?php

    function __autoload($class){
        if(file_exists($class . ".php")){
            require_once $class . ".php";
        }
    }

Than just include something.php on all the pages you need like :

<?php

    require_once 'something.php';

    $class1 = new Class1();
    $class2 = new Class2();