一个PHP文件如何使用另一个提供的类

Question

I need to do a task involving a PHP class and some sample code which is supposed to run the class. code bellow.

autoloader.php

<?php

/**
 * A basic PSR style autoloader
 */
class AutoLoader
{
    protected $dir;
    protected $ext;

    public function __construct($dir, $ext = '.php')
    {
        $this->dir = rtrim($dir, DIRECTORY_SEPARATOR);
        $this->ext = $ext;
    }

    public static function register($dir, $ext = '.php')
    {
        $autoloader = new static($dir, $ext);
        spl_autoload_register([$autoloader, 'load']);

        return $autoloader;
    }

    public function load($class)
    {
        $dir = $this->dir;

        if ($ns = $this->get_namespace($class)) {
            $dir .= DIRECTORY_SEPARATOR.str_replace('\\', DIRECTORY_SEPARATOR, $ns);
        }

        $inc_file = $dir.DIRECTORY_SEPARATOR.$this->get_class($class).$this->ext;

        if (file_exists($inc_file)) {
            require_once $inc_file;
        }
    }

    // Borrowed from github.com/borisguery/Inflexible
    protected static function get_class($value)
    {
        $className = trim($value, '\\');

        if ($lastSeparator = strrpos($className, '\\')) {
            $className = substr($className, 1 + $lastSeparator);
        }

        return $className;
    }

    // Borrowed from github.com/borisguery/Inflexible
    public static function get_namespace($fqcn)
    {
        if ($lastSeparator = strrpos($fqcn, '\\')) {
            return trim(substr($fqcn, 0, $lastSeparator + 1), '\\');
        }

        return '';
    }
}

run.php

<?php

/* Register a basic autoloader */
require_once 'AutoLoader.php';
AutoLoader::register('src');

/* Create a packer */
$packer = new \Candidate\BoxPacker\DeveloperTestPacker();

/* Create some test boxes */
$boxes = [];
// Create your boxes here

/* Add boxes to packer */
$packer->addBoxes($boxes);

/* Create some test items */
$items = [];
// Create your items here

/* Add items to packer */
$packer->addItems($items);

/* Pack */
$packed_boxes = $packer->pack();

/* Output - var_dump is fine */
var_dump($packed_boxes);

i understand that the require statement in run.php loads the autoloader.php script but that is the only thing about this which makes sense to me.

my questions are as follows

1) what does AutoLoader::register('src'); do?

2) $packer = new \Candidate\BoxPacker\DeveloperTestPacker(); creates a new packer object, but what is this object? the autoloader.php file does not make any reference to \Candidate\BoxPacker\DeveloperTestPacker().

3) The lines $packer->addBoxes($boxes);, $packer->addItems($items);, $packer->pack(); seam to call the methods addBoxes(), addItems() and pack() of the instance of a class referenced to by $packer.

However none of these methods appear in the autoloader class in the autoloader.php file. and even if they did, $packer references an instance of \Candidate\BoxPacker\DeveloperTestPacker not an instance of autoloader.

Can someone explain to me what is happening here?

Answer 1

1. AutoLoader::register('src'); instantiated a new instance of the Autoload class, providing the src directory as a parameter, and then

   spl_autoload_register([$autoloader, 'load']);
   

   registers the load method in the Autoloader class as an implementation of __autoload

2. Now when you attempt to use a class that has not been defined in scope, because you have registered an autoloader, it will attempt to look for the class in the src directory using the load method in the Autoloader class. If the autoloader finds the class, it uses PHP's include method to bring the class into scope so that you can then instantiate a new instance of it.

3. The methods you mention are defined in the \Candidate\BoxPacker\DeveloperTestPacker class