0. PSR-0 --- 自动加载

<?php

define('BASEDIR',__DIR__);

include BASEDIR . '/IMooc/Loader.php';
spl_autoload_register('\\IMooc\\Loader::autoload');

IMooc\Object::test();

App\Controller\Home\Index::test();

<?php

namespace IMooc;

class Loader
{
static function autoload($class)
{
require BASEDIR . '/' . str_replace('\\','/',$class)  . '.php';
}
}

<?php

//命名空间必须与绝对路径一致
//这个文件除了 class 之外，不能有其他可执行代码
namespace IMooc;

class Object
{
static function test()
{
echo __METHOD__,'<br/>';
}
}

<?php

namespace App\Controller\Home;

class Index
{
static function test()
{
echo __METHOD__,'<br/>';
}
}

PSR是Proposing a Standards Recommendation（提出标准建议）的缩写，是由
PHP Framework Interoperability Group
（PHP通用性框架小组，简称PHP-FIG）发起的，
通过他们命名就可以看出，这是个主要是针对框架通用性
而做努力的开放性小组，他们的在Github上有自己的仓库地址，
目前只有一个被接受的标准，那就是PSR-0标准，标准定义了
PHP自动加载的命名规范和文件路径规范。
针对PSR-0标准主要提到了以下几点：

<?php

public static function autoload($className)
{
// 例如，$className = '\namespace\package_name\Class_Name';

$className = ltrim($className,'\\');  // 去掉最左边的 \ ,namespace\package_name\Class_Name
$fileName = '';
$namespace = '';
if($lastNoPos = strrpos($className,'\\')){  // 找到最右边的 \,$lastNoPos = 22
$namespace = substr($className,0,$lastNoPos);  // namespace\package_name
$className = substr($className,$lastNoPos+1);  // Class_Name
//            $a = str_replace('\\',DIRECTORY_SEPARATOR,$namespace);
$fileName = str_replace('\\',DIRECTORY_SEPARATOR,$namespace) . DIRECTORY_SEPARATOR;
}
$fileName .= str_replace('_',DIRECTORY_SEPARATOR,$className) . '.php';  // $fileName = namespace\package_name\Class\Name.php;
require $fileName;
}

<?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;
}
}
}