php 实现工厂模式 实例[通俗易懂]

<?php

//定义一个抽象类
abstract class Operation
{
    protected $numA = 0;
    protected $numB = 0;
    protected $result = 0;

    //构造方法获取到传入的$a 和 $b
    public function __construct($a, $b)
    {
        $this->numA = $a;
        $this->numB = $b;
    }

    //抽象方法所有子类必须实现该方法
    protected abstract function getResult();
}

//加法运算
class OperationAdd extends Operation
{
    //实现父类的getResult方法
    public function getResult()
    {
        $this->result = $this->numA + $this->numB;
        return $this->result;
    }
}

//减法运算
class OperationSub extends Operation
{
    //实现父类的getResult方法
    public function getResult()
    {
        $this->result = $this->numA - $this->numB;
        return $this->result;
    }
}

//工厂类
class OperationFactory
{
    //创建保存实例的静态成员变量
    private static $obj;
    //创建实例的静态方法
    public static function CreateOperation($type, $a, $b)
    {
        switch ($type) {
            case "+":
                self::$obj = new OperationAdd($a, $b);
                break;
            case "-":
                self::$obj = new OperationSub($a, $b);
                break;
        }
        return self::$obj;
    }
}

$obj = OperationFactory::CreateOperation('+', 10, 10);
var_dump($obj->getResult());