PSR-0 自动加载规范

Deprecated - As of 2014-10-21 PSR-0 has been marked as deprecated. 
PSR-4 is now recommended as an alternative.

在 2014-10-21 被标记为已过期。
推荐使用 PSR-4 规范

The following describes the mandatory requirements that must be adhered to for autoloader interoperability.

Mandatory (规范)

  • A fully-qualified namespace and class must have the following structure <Vendor Name>()*

  • Each namespace must have a top-level namespace (“Vendor Name”).(任意命名空间必须拥有一个顶级命名空间)

  • Each namespace can have as many sub-namespaces as it wishes.(任意命名空间可以拥有任意多的子命名空间)

  • Each namespace separator is converted to a DIRECTORY_SEPARATOR when loading from the file system.(任意一个命名空间分隔符都要转换成目录分隔符 即 命名空间必须与绝对路径一致)

  • Each _ character in the CLASS NAME is converted to a DIRECTORY_SEPARATOR. The _ character has no special meaning in the namespace. (在类名中的 _ 符号,只有被转换成目录分隔符的含义)

  • The fully-qualified namespace and class is suffixed with .php when loading from the file system.

  • Alphabetic characters in vendor names, namespaces, and class names may be of any combination of lower case and upper case.

Examples

  • \Doctrine\Common\IsolatedClassLoader => /path/to/project/lib/vendor/Doctrine/Common/IsolatedClassLoader.php
  • \Symfony\Core\Request => /path/to/project/lib/vendor/Symfony/Core/Request.php
  • \Zend\Acl => /path/to/project/lib/vendor/Zend/Acl.php
  • \Zend\Mail\Message => /path/to/project/lib/vendor/Zend/Mail/Message.php

Underscores in Namespaces and Class Names (下划线在命名空间和类名的用例)

  • \namespace\package\Class_Name => /path/to/project/lib/vendor/namespace/package/Class/Name.php
  • \namespace\package_name\Class_Name => /path/to/project/lib/vendor/namespace/package_name/Class/Name.php

The standards we set here should be the lowest common denominator for painless autoloader interoperability. You can test that you are following these standards by utilizing this sample SplClassLoader implementation which is able to load PHP 5.3 classes.

Example Implementation (实现方法)

<?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');

SplClassLoader Implementation

<?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 = '\\';

    /**
     * Creates a new <tt>SplClassLoader</tt> that loads classes of the
     * specified namespace.
     * 
     * @param string $ns The namespace to use.
     */
    public function __construct($ns = null, $includePath = null)
    {
        $this->_namespace = $ns;
        $this->_includePath = $includePath;
    }

    /**
     * Sets the namespace separator used by classes in the namespace of this class loader.
     * 
     * @param string $sep The separator to use.
     */
    public function setNamespaceSeparator($sep)
    {
        $this->_namespaceSeparator = $sep;
    }

    /**
     * Gets the namespace seperator used by classes in the namespace of this class loader.
     *
     * @return void
     */
    public function getNamespaceSeparator()
    {
        return $this->_namespaceSeparator;
    }

    /**
     * Sets the base include path for all class files in the namespace of this class loader.
     * 
     * @param string $includePath
     */
    public function setIncludePath($includePath)
    {
        $this->_includePath = $includePath;
    }

    /**
     * Gets the base include path for all class files in the namespace of this class loader.
     *
     * @return string $includePath
     */
    public function getIncludePath()
    {
        return $this->_includePath;
    }

    /**
     * Sets the file extension of class files in the namespace of this class loader.
     * 
     * @param string $fileExtension
     */
    public function setFileExtension($fileExtension)
    {
        $this->_fileExtension = $fileExtension;
    }

    /**
     * Gets the file extension of class files in the namespace of this class loader.
     *
     * @return string $fileExtension
     */
    public function getFileExtension()
    {
        return $this->_fileExtension;
    }

    /**
     * Installs this class loader on the SPL autoload stack.
     */
    public function register()
    {
        spl_autoload_register(array($this, 'loadClass'));
    }

    /**
     * Uninstalls this class loader from the SPL autoloader stack.
     */
    public function unregister()
    {
        spl_autoload_unregister(array($this, 'loadClass'));
    }

    /**
     * Loads the given class or interface.
     *
     * @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;
        }
    }
}