<?php 
/** 
* 職責(zé)鏈模式 
* 
* 為解除請求的發(fā)送者和接收者之間的耦合,而使用多個對象都用機會處理這個請求,將這些對象連成一條鏈,并沿著這條鏈傳遞該請求,直到有一個對象處理它 
* 
*/ 
abstract class Handler 
{ 
protected $_handler = null; 
public function setSuccessor($handler) 
{ 
$this->_handler = $handler; 
} 
abstract function handleRequest($request); 
} 
class ConcreteHandlerZero extends Handler 
{ 
public function handleRequest($request) 
{ 
if($request == 0) 
{ 
echo "0<br/>"; 
} else { 
$this->_handler->handleRequest($request); 
} 
} 
} 
class ConcreteHandlerOdd extends Handler 
{ 
public function handleRequest($request) 
{ 
if($request % 2) 
{ 
echo $request." is odd<br/>"; 
} else { 
$this->_handler->handleRequest($request); 
} 
} 
} 
class ConcreteHandlerEven extends Handler 
{ 
public function handleRequest($request) 
{ 
if(!($request % 2)) 
{ 
echo $request." is even<br/>"; 
} else { 
$this->_handler->handleRequest($request); 
} 
} 
} 
// 實例一下 
$objZeroHander = new ConcreteHandlerZero(); 
$objEvenHander = new ConcreteHandlerEven(); 
$objOddHander = new ConcreteHandlerOdd(); 
$objZeroHander->setSuccessor($objEvenHander); 
$objEvenHander->setSuccessor($objOddHander); 
foreach(array(2,3,4,5,0) as $row) 
{ 
$objZeroHander->handleRequest($row); 
}