面向对象---工厂模式

//设计模式:工厂模式
/*class suanshu
{
    public $a;
    public $b;
    
    function jia()
    {
        return $this->a+$this->b; 
    }
    function jian()
    {    
        return $this->a-$this->b;
    }
    function cheng()
    {
        return $this->a*$this->b;
    }
    function chu()
    {
        return $This->a/$this->b;    
    }
    function quyu()
    {
        return $this->a%$this->b;
    }
}
$r=new suanshu();
$r->a="5";
$r->b=9;
echo $r->quyu();*/
//大类分子类
class suanshu    
{
    public $a;
    public $b;
    
    function yunsuan(){}
}
class jia extends suanshu
{
    function yunsuan()
    {
        return $this->a+$this->b;
        }
    }
class jian extends suanshu
{
    function yunsuan()
    {
          return $this->a-$this->b;
        }
    }
class cheng extends suanshu
{
    function yunsuan()
    {
        return $this->a*$this->b;
        }
    }
$r=new jia();
$r->a=1;
$r->b=1;
echo $r->yunsuan()."<br />";
$r=new jian();
$r->a=1;
$r->b=1;
echo $r->yunsuan();

//工厂类 对创建的对象进行优化，不用记住对象名，只需要记住符号或是代号就好。
class gongchang
{
    static function duixiang($a)
    {
        switch($a)
        {    
            case "+":
                return new jia(); 
                break;
            case "-":
                return new jian();
                break;
            case "*":
                return new cheng();
                break;
            case "/":
                return new chu();
                break;
        }
    }
}
$r=gongchang::duixiang("-");//重点是这句话
$r->a=10;
$r->b=5;
echo $r->yunsuan();