PHP yii框架源碼閱讀（二） 整體執行流程分析

一 程序入口

<?php
    
// change the following paths if necessary 
$yii=dirname(__FILE__).'/http://www.cnblogs.com/framework/yii.php';
$config=dirname(__FILE__).'/protected/config/main.php';
    
// remove the following line when in production mode
// defined('YII_DEBUG') or define('YII_DEBUG',true);
    
require_once($yii);
Yii::createWebApplication($config)->run();

require_once($yii) 語句包含了yii.php 文件，該文件是Yii bootstrap file，包含了 yiibase的基礎類，yii完全繼承了yiibase

<?php
/**
 * Yii bootstrap file.
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @link http://www.yiiframework.com/
 * @copyright Copyright &copy; 2008-2011 Yii Software LLC
 * @license http://www.yiiframework.com/license/
 * @version $Id: yii.php 2799 2011-01-01 19:31:13Z qiang.xue $
 * @package system
 * @since 1.0
 */
    
require(dirname(__FILE__).'/YiiBase.php');
    
/**
 * Yii is a helper class serving common framework functionalities.
 *
 * It encapsulates {@link YiiBase} which provides the actual implementation.
 * By writing your own Yii class, you can customize some functionalities of YiiBase.
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @version $Id: yii.php 2799 2011-01-01 19:31:13Z qiang.xue $
 * @package system
 * @since 1.0
 */
class Yii extends YiiBase
{
}

在 YiiBase 類中 定義了一些 比如：

public static function createWebApplication($config=null) // 創建啟動
    
public static function import($alias,$forceInclude=false) // 類導入
    
public static function createComponent($config) // 創建組件
    
public static function setApplication($app)  // 創建類的實例 yii::app()

二 自動加載機制

還有比較重要的yii自動加載機制，在yiibase的最後引用了php的標准庫函數 spl_autoload_register(array('YiiBase','autoload')) 調用框架中的autoload方法

/**
     * Class autoload loader.
     * This method is provided to be invoked within an __autoload() magic method.
     * @param string $className class name
     * @return boolean whether the class has been loaded successfully
     */
    public static function autoload($className)
    {
        // use include so that the error PHP file may appear
        if(isset(self::$classMap[$className]))
            include(self::$classMap[$className]);
        else if(isset(self::$_coreClasses[$className]))
            include(YII_PATH.self::$_coreClasses[$className]);
        else
        {
            // include class file relying on include_path
            if(strpos($className,'\\')===false)  // class without namespace
            {
                if(self::$enableIncludePath===false)
                {
                    foreach(self::$_includePaths as $path)
                    {
                        $classFile=$path.DIRECTORY_SEPARATOR.$className.'.php';
                        if(is_file($classFile))
                        {
                            include($classFile);
                            break;
                        }
                    }
                }
                else
                    include($className.'.php');
            }
            else  // class name with namespace in PHP 5.3
            {
                $namespace=str_replace('\\','.',ltrim($className,'\\'));
                if(($path=self::getPathOfAlias($namespace))!==false)
                    include($path.'.php');
                else
                    return false;
            }
            return class_exists($className,false) || interface_exists($className,false);
        }
        return true;
    }

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