ClassLoader.php

<?php
/**
 * PHP 5
 *
 * CakePHP(tm) : Rapid Development Framework (http://cakephp.org)
 * Copyright 2005-2011, Cake Software Foundation, Inc. (http://cakefoundation.org)
 *
 * Licensed under The MIT License
 * Redistributions of files must retain the above copyright notice.
 *
 * @copyright     Copyright 2005-2011, Cake Software Foundation, Inc. (http://cakefoundation.org)
 * @link          http://cakephp.org CakePHP(tm) Project
 * @since         CakePHP(tm) v 3.0
 * @license       MIT License (http://www.opensource.org/licenses/mit-license.php)
 */
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], $baseDir);
		} else {
			array_push($this->_prefixes[$prefix], $baseDir);
		}
	}

/**
 * Loads the class file for a given class name.
 *
 * @param string $class The fully-qualified class name.
 * @return mixed The mapped file name on success, or boolean false on
 * failure.
 */
	public function loadClass($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 $relativeClass The relative class name.
 * @return mixed Boolean false if no mapped file can be loaded, or the
 * name of the mapped file that was loaded.
 */
	protected function _loadMappedFile($prefix, $relativeClass) {
		if (!isset($this->_prefixes[$prefix])) {
			return false;
		}

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

}