<?php
/**
 * 【策略模式】----和“简单工厂”模式很相似
 * 根据不同运算符计算两个数的运算结果
 * 常规方式就是判断运算符然后进行if...else的操作
 * 现在使用“策略模式”
 */

header("Content-type: text/html; charset=utf-8");

if(isset($_POST['js']) && !empty($_POST['js'])){
    /*接口，和四个真实计算器*/
    interface Math{
        public function calc($op1,$op2);
    }
    class Jia implements Math{
        public function calc($op1, $op2){
            return $op1+$op2;
        }
    }
    class Jian implements Math{
        public function calc($op1, $op2){
            return $op1-$op2;
        }
    }
    class Cheng implements Math{
        public function calc($op1, $op2){
            return $op1*$op2;
        }
    }
    class Chu implements Math{
        public function calc($op1, $op2){
            return $op1/$op2;
        }
    }

    /*封装一个虚拟计算器*/
    class CMath{
        protected $jisuan = null;
        //$objType 对应的真实计算器的 Jia/Jian/Cheng/Chu
        public function __construct($type){
            if($type==1){
                $objType = 'Jia';
            }elseif($type==2){
                $objType = 'Jian';
            }elseif($type==3){
                $objType = 'Cheng';
            }elseif($type==4){
                $objType = 'Chu';
            }else{
                exit('Error...');
            }
            $this->jisuan = new $objType();
        }
        public function jsq($num1,$num2){
            return $this->jisuan->calc($num1,$num2);
        }
    }

    /*开始调用*/
    $js = $_POST['js'];
    $cmath = new CMath($js);
    $res = $cmath->jsq($_POST['num1'], $_POST['num2']);
    echo $res;

}

?>

<form action="?" method="post">
<input type="text" name="num1">
<select name="js">
    <option value="1">+</option>
    <option value="2">-</option>
    <option value="3">*</option>
    <option value="4">/</option>
</select>
<input type="text" name="num2">
<button type="submit">提交</button>
</form>