PSR-0対応Autoloader

autoload.53.php

<?php
namespace Acme;

require_once realpath(__DIR__ . '/vendor/k-holy/src/Holy/Loader.php');

// PHP 5.3 (using setter)
spl_autoload_register(\Holy\Loader::getInstance()
->set('Holy', realpath(__DIR__ . '/vendor/k-holy/src'))
->set('Acme', realpath(__DIR__ . '/app/src'))
, true, true);

autoload.54.php

<?php
namespace Acme;

require_once realpath(__DIR__ . '/vendor/k-holy/src/Holy/Loader.php');

// PHP5.4 Array short syntax
spl_autoload_register(\Holy\Loader::getInstance([
    'Holy' => [realpath(__DIR__ . '/vendor/k-holy/src')],
    'Acme' => [realpath(__DIR__ . '/app/src')],
]), true, true);

Loader.php

<?php
/**
 * PHP versions 5
 *
 * @copyright  2011 k-holy <k.holy74@gmail.com>
 * @author     k.holy74@gmail.com
 * @license    http://www.opensource.org/licenses/mit-license.php  The MIT License (MIT)
 */
namespace Holy;

/**
 * Loader
 *
 * @author     k.holy74@gmail.com
 */
class Loader
{

    const FILE_EXTENSION = '.php';
    const NAMESPACE_SEPARTOR= '\\';
    protected $vendors = array();

    protected function __construct(array $vendors = array())
    {
        $this->init($vendors);
    }

    public static function getInstance(array $vendors = array())
    {
        return new self($vendors);
    }

    public function __invoke($className)
    {
        return $this->load($className);
    }

    public function init(array $vendors = array())
    {
        $this->vendors = $vendors;
    }

    /**
     * ベンダー名および設置パス、拡張子を設定します。
     * @param string ベンダー名(namespace)
     * @param string 設置パス
     * @param string 拡張子
     */
    public function set($name, $includeDir, $fileExtension=null)
    {
        $includeDir = rtrim($includeDir, '\\/');
        if ('\\' === DIRECTORY_SEPARATOR) {
            $includeDir = str_replace('/', '\\', $includeDir);
        }
        $this->vendors[$name] = array($includeDir, $fileExtension);
        return $this;
    }

    /**
     * 指定されたクラスのファイルを読み込みます。
     * @param string クラス名
     */
    public function load($className)
    {
        if (false === ($filePath = $this->findFile($className))) {
            return false;
        }
        return require $filePath;
    }

    protected function findFile($className)
    {
        $baseName = ltrim($className, self::NAMESPACE_SEPARTOR);
        $useNamespace = false;
        if (false !== ($pos = strrpos($baseName, self::NAMESPACE_SEPARTOR))) {
            $useNamespace = true;
            $namespace = substr($baseName, 0, $pos);
            $baseName = substr($baseName, $pos + 1);
            $fileName  = str_replace(self::NAMESPACE_SEPARTOR, DIRECTORY_SEPARATOR, $namespace)
                . DIRECTORY_SEPARATOR . str_replace('_', DIRECTORY_SEPARATOR, $baseName);
        } else {
            $fileName  = str_replace('_', DIRECTORY_SEPARATOR, $baseName);
        }
        $requirePath = null;
        foreach ($this->vendors as $name => $info) {
            $includeDir = $info[0];
            $fileExtension = (isset($info[1])) ? $info[1] : self::FILE_EXTENSION;
            if (0 === strpos(($useNamespace) ? $namespace : $baseName, $name)) {
                $path = $includeDir . DIRECTORY_SEPARATOR . $fileName . $fileExtension;
                if (file_exists($path)) {
                    $requirePath = $path;
                    break;
                }
            }
        }
        if (is_null($requirePath)) {
            $requirePath = stream_resolve_include_path($fileName . self::FILE_EXTENSION);
        }
        return $requirePath;
    }

}

LoaderTest.php

<?php
namespace Holy\Tests;

use Holy\Loader;

/**
 * LoaderTest
 *
 * @author     k.holy74@gmail.com
 */
class LoaderTest extends \PHPUnit_Framework_TestCase
{

    private $defaultLoaders = array();
    private $defaultIncludePath = null;
    private $loader = null;

    public function setUp()
    {
        $this->defaultLoaders = spl_autoload_functions();
        if (!is_array($this->defaultLoaders)) {
            $this->defaultLoaders = array();
        }
        $this->defaultIncludePath = get_include_path();
        $this->loader = Loader::getInstance();
        $this->loader->init();
    }

    public function tearDown()
    {
        $loaders = spl_autoload_functions();
        if (is_array($loaders)) {
            foreach ($loaders as $loader) {
                spl_autoload_unregister($loader);
            }
        }
        if (is_array($this->defaultLoaders)) {
            foreach ($this->defaultLoaders as $loader) {
                spl_autoload_register($loader);
            }
        }
        set_include_path($this->defaultIncludePath);
    }

    public function testCreateNewInstance()
    {
        $this->assertNotSame($this->loader, Loader::getInstance());
    }

    public function testLoadNamespacedClass()
    {
        $this->loader
            ->set('LoadSample', realpath(__DIR__ . '/LoaderTest/lib/vendor'))
            ->load('\LoadSample\Foo');
        $this->assertInstanceOf('\LoadSample\Foo', new \LoadSample\Foo());

        $this->loader->load('\LoadSample\Foo\Bar');
        $this->assertInstanceOf('\LoadSample\Foo\Bar', new \LoadSample\Foo\Bar());

        $this->loader->load('\LoadSample\Foo\Bar\Baz');
        $this->assertInstanceOf('\LoadSample\Foo\Bar\Baz', new \LoadSample\Foo\Bar\Baz());
    }

    public function testloadLegacyClassWithDirectoryAndExtension()
    {
        $this->loader
            ->set('Smorty', realpath(__DIR__ . '/LoaderTest/lib/vendor/Smorty/libs'), '.class.php')
            ->load('Smorty');
        $this->assertInstanceOf('\Smorty', new \Smorty());
    }

    public function testAutoloadLegacyClassInIncludePath()
    {
        set_include_path(realpath(__DIR__ . '/LoaderTest/include_path'));
        $this->loader->load('\PearStyleClass_Example');
        $this->assertInstanceOf('\PearStyleClass_Example', new \PearStyleClass_Example());
    }

    public function testAutoload()
    {
        $this->loader
            ->set('AutoloadSample', realpath(__DIR__ . '/LoaderTest/lib/vendor'))
            ->set('Smorty'        , realpath(__DIR__ . '/LoaderTest/lib/vendor/Smorty/libs'), '.class.php');
        spl_autoload_register(array($this->loader, 'load'), true, true);
        set_include_path(realpath(__DIR__ . '/LoaderTest/include_path'));

        $this->assertInstanceOf('\AutoloadSample\Foo', new \AutoloadSample\Foo());
        $this->assertInstanceOf('\AutoloadSample\Foo\Bar', new \AutoloadSample\Foo\Bar());
        $this->assertInstanceOf('\AutoloadSample\Foo\Bar\Baz', new \AutoloadSample\Foo\Bar\Baz());
        $this->assertInstanceOf('\Smorty', new \Smorty());
        $this->assertInstanceOf('\PearStyleClass_Example', new \PearStyleClass_Example());
    }

    public function testAutoloadByInvokeMagicMethod()
    {
        spl_autoload_register(Loader::getInstance(array(
            'AutoloadSample' => array(realpath(__DIR__ . '/LoaderTest/lib/vendor')),
            'Smorty'         => array(realpath(__DIR__ . '/LoaderTest/lib/vendor/Smorty/libs'), '.class.php'),
        )), true, true);
        set_include_path(realpath(__DIR__ . '/LoaderTest/include_path'));

        $this->assertInstanceOf('\AutoloadSample\Foo', new \AutoloadSample\Foo());
        $this->assertInstanceOf('\AutoloadSample\Foo\Bar', new \AutoloadSample\Foo\Bar());
        $this->assertInstanceOf('\AutoloadSample\Foo\Bar\Baz', new \AutoloadSample\Foo\Bar\Baz());
        $this->assertInstanceOf('\Smorty', new \Smorty());
        $this->assertInstanceOf('\PearStyleClass_Example', new \PearStyleClass_Example());
    }


}

https://gist.github.com/1127033 ここからの改良。
やはりローダー自身がspl_autoload_register()するのはおかしいよね、ということでこうしました。