ClassLoader.php

<?php
/**
 * CakePHP(tm) : Rapid Development Framework (https://cakephp.org)
 * Copyright 2005-2011, Cake Software Foundation, Inc. (https://cakefoundation.org)
 *
 * Licensed under The MIT License
 * Redistributions of files must retain the above copyright notice.
 *
 * @copyright     Copyright (c) Cake Software Foundation, Inc. (https://cakefoundation.org)
 * @link          https://cakephp.org CakePHP(tm) Project
 * @since         3.0.0
 * @license       https://opensource.org/licenses/mit-license.php MIT License
 */
namespace Cake\Core;

/**
 * ClassLoader
 */
class ClassLoader
{
    /**
     * An associative array where the key is a namespace prefix and the value
     * is an array of base directories for classes in that namespace.
     *
     * @var array
     */
    protected $_prefixes = [];

    /**
     * Register loader with SPL autoloader stack.
     *
     * @return void
     */
    public function register()
    {
        spl_autoload_register([$this, 'loadClass']);
    }

    /**
     * Adds a base directory for a namespace prefix.
     *
     * @param string $prefix The namespace prefix.
     * @param string $baseDir A base directory for class files in the
     * namespace.
     * @param bool $prepend If true, prepend the base directory to the stack
     * instead of appending it; this causes it to be searched first rather
     * than last.
     * @return void
     */
    public function addNamespace($prefix, $baseDir, $prepend = false)
    {
        $prefix = trim($prefix, '\\') . '\\';

        $baseDir = rtrim($baseDir, '/') . DIRECTORY_SEPARATOR;
        $baseDir = rtrim($baseDir, DIRECTORY_SEPARATOR) . '/';

        if (!isset($this->_prefixes[$prefix])) {
            $this->_prefixes[$prefix] = [];
        }

        if ($prepend) {
            array_unshift($this->_prefixes[$prefix], $baseDir);
        } else {
            $this->_prefixes[$prefix][] = $baseDir;
        }
    }

    /**
     * Loads the class file for a given class name.
     *
     * @param string $class The fully-qualified class name.
     * @return string|false The mapped file name on success, or boolean false on
     * failure.
     */
    public function loadClass($class)
    {
        $prefix = $class;

        while (($pos = strrpos($prefix, '\\')) !== false) {
            $prefix = substr($class, 0, $pos + 1);
            $relativeClass = substr($class, $pos + 1);

            $mappedFile = $this->_loadMappedFile($prefix, $relativeClass);
            if ($mappedFile) {
                return $mappedFile;
            }

            $prefix = rtrim($prefix, '\\');
        }

        return false;
    }

    /**
     * Load the mapped file for a namespace prefix and relative class.
     *
     * @param string $prefix The namespace prefix.
     * @param string $relativeClass The relative class name.
     * @return string|false Boolean false if no mapped file can be loaded, or the
     * name of the mapped file that was loaded.
     */
    protected function _loadMappedFile($prefix, $relativeClass)
    {
        if (!isset($this->_prefixes[$prefix])) {
            return false;
        }

        foreach ($this->_prefixes[$prefix] as $baseDir) {
            $file = $baseDir . str_replace('\\', DIRECTORY_SEPARATOR, $relativeClass) . '.php';

            if ($this->_requireFile($file)) {
                return $file;
            }
        }

        return false;
    }

    /**
     * If a file exists, require it from the file system.
     *
     * @param string $file The file to require.
     * @return bool True if the file exists, false if not.
     */
    protected function _requireFile($file)
    {
        if (file_exists($file)) {
            require $file;

            return true;
        }

        return false;
    }
}