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=10;
$r->b=5;
echo $r->Suan();

制返回对象只能是一个