PHP-自动加载规范

简单实现

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<?php
function autoload($className)
{
    $className = ltrim($className, '\\');
    $fileName  = '';
    $namespace = '';
    if ($lastNsPos = strrpos($className, '\\')) {
        $namespace = substr($className, 0, $lastNsPos);
        $className = substr($className, $lastNsPos + 1);
        $fileName  = str_replace('\\', DIRECTORY_SEPARATOR, $namespace) . DIRECTORY_SEPARATOR;
    }
    $fileName .= str_replace('_', DIRECTORY_SEPARATOR, $className) . '.php';

    require $fileName;
}
spl_autoload_register('autoload');

摘录自：https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-0.md#example-implementation

SplClassLoader 实现

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<?php
/*
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * This software consists of voluntary contributions made by many individuals
 * and is licensed under the MIT license. For more information, see
 * <http://www.doctrine-project.org>.
 */
 
/**
 * SplClassLoader implementation that implements the technical interoperability
 * standards for PHP 5.3 namespaces and class names.
 *
 * http://groups.google.com/group/php-standards/web/psr-0-final-proposal?pli=1
 *
 *     // Example which loads classes for the Doctrine Common package in the
 *     // Doctrine\Common namespace.
 *     $classLoader = new SplClassLoader('Doctrine\Common', '/path/to/doctrine');
 *     $classLoader->register();
 *
 * @license http://www.opensource.org/licenses/mit-license.html  MIT License
 * @author Jonathan H. Wage <jonwage@gmail.com>
 * @author Roman S. Borschel <roman@code-factory.org>
 * @author Matthew Weier O'Phinney <matthew@zend.com>
 * @author Kris Wallsmith <kris.wallsmith@gmail.com>
 * @author Fabien Potencier <fabien.potencier@symfony-project.org>
 */
class SplClassLoader
{
    private $_fileExtension = '.php';
    private $_namespace;
    private $_includePath;
    private $_namespaceSeparator = '\\';
    /**
     * 创建一个新的SplClassLoader，用于加载指定命名空间。
     * 
     * @param string $ns The namespace to use.
     */
    public function __construct($ns = null, $includePath = null)
    {
        $this->_namespace = $ns;
        $this->_includePath = $includePath;
    }
    /**
     * 设置这个类加载器的命名空间中类使用的命名空间分隔符。
     * 
     * @param string $sep The separator to use.
     */
    public function setNamespaceSeparator($sep)
    {
        $this->_namespaceSeparator = $sep;
    }
    /**
     * 获取这个类加载器的命名空间中类使用的命名空间分隔符。
     *
     * @return void
     */
    public function getNamespaceSeparator()
    {
        return $this->_namespaceSeparator;
    }
    /**
     * 设置此类加载器命名空间中所有类文件的基包含路径。
     * 
     * @param string $includePath
     */
    public function setIncludePath($includePath)
    {
        $this->_includePath = $includePath;
    }
    /**
     * 获取此类加载器命名空间中所有类文件的基包含路径。
     *
     * @return string $includePath
     */
    public function getIncludePath()
    {
        return $this->_includePath;
    }
    /**
     * 在这个类加载器的命名空间中设置类文件的文件扩展名。
     * 
     * @param string $fileExtension
     */
    public function setFileExtension($fileExtension)
    {
        $this->_fileExtension = $fileExtension;
    }
    /**
     * 获取这个类加载器的命名空间中设置类文件的文件扩展名。
     *
     * @return string $fileExtension
     */
    public function getFileExtension()
    {
        return $this->_fileExtension;
    }
    /**
     * 将此类加载器安装在SPL自动加载堆栈上。
     */
    public function register()
    {
        spl_autoload_register(array($this, 'loadClass'));
    }
    /**
     * 从SPL自动加载程序堆栈卸载此类加载程序。
     */
    public function unregister()
    {
        spl_autoload_unregister(array($this, 'loadClass'));
    }
    /**
     * 加载给定的类或接口。
     *
     * @param string $className The name of the class to load.
     * @return void
     */
    public function loadClass($className)
    {
        if (null === $this->_namespace || $this->_namespace.$this->_namespaceSeparator === substr($className, 0, strlen($this->_namespace.$this->_namespaceSeparator))) {
            $fileName = '';
            $namespace = '';
            if (false !== ($lastNsPos = strripos($className, $this->_namespaceSeparator))) {
                $namespace = substr($className, 0, $lastNsPos);
                $className = substr($className, $lastNsPos + 1);
                $fileName = str_replace($this->_namespaceSeparator, DIRECTORY_SEPARATOR, $namespace) . DIRECTORY_SEPARATOR;
            }
            $fileName .= str_replace('_', DIRECTORY_SEPARATOR, $className) . $this->_fileExtension;
            require ($this->_includePath !== null ? $this->_includePath . DIRECTORY_SEPARATOR : '') . $fileName;
        }
    }
}

摘录自：https://gist.github.com/jwage/221634