Example Explanation of Automatic Loading of Classes in php Project

Main function: spl_autoload_register ()-Registers the given function as an implementation of __autoload ()

Register the function in the SPL __autoload function queue. If the functions in the queue have not been activated, they are activated.

If the __autoload () function has been implemented in your program, it must be explicitly registered in the __autoload () queue. Because the spl_autoload_register () function replaces the __autoload () function in Zend Engine with spl_autoload () or spl_autoload_call ().

If multiple autoload functions are required, spl_autoload_register () satisfies such requirements. It actually creates a queue of autoload functions, which are executed one by one in the order in which they were defined. In contrast, __autoload () can only be defined once.

<?php

// $class  Class name 
function autoloader_1($class) {
  include 'classes/' . $class . '.class.php';
}

function autoloader_2($class) {
  include 'classes/' . $class . '.class.php';
}

//  Can be used multiple times, but  __autoload()  Function can only use the 1 Times. 
spl_autoload_register('autoloader_1');
spl_autoload_register('autoloader_2');

//  Or, since  PHP 5.3.0  Can be used from now on 1 Anonymous function 
spl_autoload_register(function ($class) {
  include 'classes/' . $class . '.class.php';
});

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