PHP的Yii框架中YiiBase入口类的扩展写法示例

<?php
// change the following paths if necessary
$yii=dirname(__file__).'/../yii/framework/yii.php';
$config=dirname(__file__).'/protected/config/main.php';
// remove the following lines when in production mode
defined('yii_debug') or define('yii_debug',true);
// specify how many levels of call stack should be shown in each log message
defined('yii_trace_level') or define('yii_trace_level',3);
require_once($yii);
yii::createwebapplication($config)->run();

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>
 * @package system
 * @since 1.0
 */
class yii extends yiibase
{
}

yii::createwebapplication

<?php
// change the following paths if necessary
$yii=dirname(__file__).'/../yii/framework/yiibase.php';
$config=dirname(__file__).'/protected/config/main.php';
// remove the following lines when in production mode
defined('yii_debug') or define('yii_debug',true);
// specify how many levels of call stack should be shown in each log message
defined('yii_trace_level') or define('yii_trace_level',3);
require_once($yii);
//扩展基类
class yii extends yiibase{
  /**
   * 全局扩展方法：工厂函数
   * @param type $alias 类库别名
   */
  static function instance($alias){
    static $_class_ = array();
    $key = md5($alias);
    if(!isset($_class_[$key])){
      $_class_[$key] = self::createcomponent($alias);
    }
    return $_class_[$key];
  }
}
yii::createwebapplication($config)->run();

 /* yii::import()
* $alias: 要导入的类名或路径
* $forceinclude false：只导入不include类文件，true则导入并include类文件
*/
 public static function import($alias, $forceinclude = false){  
 //yii把所有的依赖放入到这个全局的$_imports数组中,名字不能重复
 //如果当前依赖已经被引入过了，那么直接返回
 if (isset(self::$_imports[$alias])) {    
    return self::$_imports[$alias];  
  }  
 //class_exists和interface_exists方法的第二个参数的值为false表示不autoload 
 if (class_exists($alias, false) || interface_exists($alias, false)) {    
   return self::$_imports[$alias] = $alias;  
 }  
 //如果传进来的是一个php5.3版本的命名空间格式的类（例如：\a\b\c.php）
 if (($pos = strrpos($alias, '\\')) !== false) {    
  //$namespace = a.b
  $namespace = str_replace('\\', '.', ltrim(substr($alias, 0, $pos), '\\')); 
  //判断a.b这个路径是否存在，或者a.b只是alias里面的一个键，调用该方法返回这个键对应的值，比如'email' => realpath(__dir__ . '/../vendor/cornernote/yii-email-module/email')
  if (($path = self::getpathofalias($namespace)) !== false) {   
    $classfile = $path . directory_separator . substr($alias, $pos + 1) . '.php';       
    if ($forceinclude) {        
     if (is_file($classfile)) {          
       require($classfile);        
      } else {          
      throw new cexception(yii::t('yii', 'alias "{alias}" is invalid. make sure it points to an existing php file and the file is readable.', array('{alias}' => $alias)));        
     }        
     self::$_imports[$alias] = $alias;      
     } else {        
     self::$classmap[$alias] = $classfile;      
    }      
    return $alias;    
  } else {      
// try to autoload the class with an autoloader      
  if (class_exists($alias, true)) {        
    return self::$_imports[$alias] = $alias;      
  } else {        
    throw new cexception(yii::t('yii', 'alias "{alias}" is invalid. make sure it points to an existing directory or file.',          array('{alias}' => $namespace)));      
  }    
  }  
 }  
if (($pos = strrpos($alias, '.')) === false) // a simple class name 
 {    
  // try to autoload the class with an autoloader if $forceinclude is true    
  if ($forceinclude && (yii::autoload($alias, true) || class_exists($alias, true))) {      
   self::$_imports[$alias] = $alias;    
   }    
  return $alias;  
 }  
 $classname = (string)substr($alias, $pos + 1);  

 $isclass = $classname !== '*';  
 if ($isclass && (class_exists($classname, false) || interface_exists($classname, false))) {    
  return self::$_imports[$alias] = $classname;  
 }  
 if (($path = self::getpathofalias($alias)) !== false) {    
   if ($isclass) {      
      if ($forceinclude) {        
         if (is_file($path . '.php')) {          
             require($path . '.php');        
         } else {          
             throw new cexception(yii::t('yii', 'alias "{alias}" is invalid. make sure it points to an existing php file and the file is readable.', array('{alias}' => $alias)));        
             }        
        self::$_imports[$alias] = $classname;      
     } else {        
        self::$classmap[$classname] = $path . '.php';      
     }      
      return $classname;    
    } 
    // $alias是'system.web.*'这样的已*结尾的路径，将路径加到include_path中
    else // a directory    
     {      
       if (self::$_includepaths === null) {    
          self::$_includepaths = array_unique(explode(path_separator, get_include_path()));  
           if (($pos = array_search('.', self::$_includepaths, true)) !== false) {          
        unset(self::$_includepaths[$pos]);        
      }      
    }      
    array_unshift(self::$_includepaths, $path);      
    if (self::$enableincludepath && set_include_path('.' . path_separator . implode(path_separator, self::$_includepaths)) === false) {        
     self::$enableincludepath = false;      
     }      
     return self::$_imports[$alias] = $path;    
    }  
  } else {    
    throw new cexception(yii::t('yii', 'alias "{alias}" is invalid. make sure it points to an existing directory or file.',      array('{alias}' => $alias)));  
    }
 }

public static function autoload($classname, $classmaponly = false){  // use include so that the error php file may appear  
if (isset(self::$classmap[$classname])) {       
  include(self::$classmap[$classname]);  
} elseif (isset(self::$_coreclasses[$classname])) {    
  include(yii_path . self::$_coreclasses[$classname]);  
} elseif ($classmaponly) {    
  return false;  
} 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($classfile);            
              if (yii_debug && basename(realpath($classfile)) !== $classname . '.php') {              
                throw new cexception(yii::t('yii', 'class name "{class}" does not match class file "{file}".', array(                '{class}' => $classname,                '{file}' => $classfile,              )));            
              }            
              break;          
           }        
       }      
   } else {        
      include($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;      
     }    
   }