php 设计模式之 单例模式

其实在工厂模式就已经应用了单例模式，从始到终它就只有一个工厂，单例模式不需要新建实例。现在写一个简单的例子。

<?php 
class boat { 
private static $instance=null; 
private $skipper; 
private $personNum=0; 
private $passengers=array(); 
private function __construct() { 
} 
public static function getInstance(){ 
if (self::$instance==null){ 
self::$instance=new boat(); 
} 
return self::$instance; 
} 
/** 
* 设置船长 
* 
* @param unknown_type $name 
*/ 
public function setSkipper($name){ 
$this->skipper=$name; 
} 
/** 
* 装人 
* 
* @param unknown_type $person 
*/ 
public function load($person){ 
if (!emptyempty($person) and $this->personNum<=5){ 
array_push($this->passengers,$person); 
$this->personNum=$this->personNum+1; 
} 
if ($this->personNum>5) { 
echo 'this boat only load 5 person!'; 
} 
} 
/** 
* 船上装了什么人 
* 
* @return unknown 
*/ 
public function whoInBoat(){ 
return $this->passengers; 
} 
} 
?> 

<?php 
include 'boat.php'; 
echo "从前有一条河，河里只有一条船，<br>"; 
$boat1=boat::getInstance();//因为只有一条船，所以只有一个实例 
echo "现在张三要到河东去,"; 
$boat1->load('张三'); 
echo "<br>现在船上坐着：<br>"; 
foreach ($boat1->whoInboat() as $who){ 
echo $who.'<br>'; 
} 
echo "<br>现在李四也要过河东去<br>"; 
$boat1->load('李四'); 
echo "现在船上坐着：<br>"; 
foreach ($boat1->whoInboat() as $who){ 
echo $who.'、'; 
} 
echo "<br><br>王五以为这条河有另一条船,<br>"; 
$boat2=boat::getInstance(); 
echo "他现在上船<br>"; 
$boat2->load('王五'); 
echo "现在船上坐着：<br>"; 
foreach ($boat1->whoInboat() as $who){ 
echo $who.'、'; 
} 
?>