php 模式

设计模式
1.单例模式
类的计划生育
1.让该类在外界无法造对象
2.让外界可以造一个对象，做一个静态方法返回对象
3.在类里面通过静态变量控

 class Dog
 {
     static $dx;
     public $test;

     private function __construct()
     {

     }

     static function DuiXiang()
     {
         //return new Dog();

         if(empty(self::$dx))
         {
             self::$dx = new Dog();
         }

         return self::$dx;
     }
 }

 $a = Dog::DuiXiang();

 $b = Dog::DuiXiang();
 $b->test="hello";

 var_dump($a);

 //工厂模式
 /*class YunSuan
 {
     public $a;
     public $b;

     function Jia()
     {
         return $a+$b;
     }
     function Jian()
     {
         return $a-$b;
     }
 }*/

 abstract class YuanSuan
 {
     public $a;
     public $b;

     function Suan()
     {
     }
 }

 class Jia extends YuanSuan
 {
     function Suan()
     {
         return $this->a+$this->b;
     }
 }

 class Jian extends YuanSuan
 {
     function Suan()
     {
         return $this->a-$this->b;
     }
 }

 class Cheng extends YuanSuan
 {
     function Suan()
     {
         return $this->a*$this->b;
     }
 }

 /*$j = new Cheng();
 $j->Suan();
 */

 class GongChang
 {
     static function ShengChan($f)
     {
         switch($f)
         {
             case "+":
                 return new Jia();
                 break;
             case "-":
                 return new Jian();
                 break;
             case "*":
                 return new Cheng();
                 break;
         }
     }
 }

 $r = GongChang::ShengChan("*");
 $r->a=;
 $r->b=;
 echo $r->Suan();

制返回对象只能是一个