工厂模式

class YunSuan
{
   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;
   }
}*/

class YunSuan
{
   public $a;
   public $b;
   
   function Suan()
   {
      echo "对两个数进行运算";
   }
}

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

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

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

工厂类
class GongChang
{
   给我一个参数，返回一个对象
   static function ChanPin($name)
   {
      switch($name)
      {
         case "+":
            return new Jia();
            break;
         case "-":
            return new Jian();
            break;
         case "*":
            return new Cheng();
            break;
      }
   }
}

$a = GongChang::ChanPin("*");
var_dump($a);