php 瀑布

<?php
// 需求分析：假设我们需要一个简单的计算器，支持加法和减法

// 设计：设计一个Calculator类
class Calculator {
    public function add($a, $b) {
        return $a + $b;
    }

    public function subtract($a, $b) {
        return $a - $b;
    }
}

// 实现：编写测试代码
$calculator = new Calculator();
echo "Addition: " . $calculator->add(5, 3) . "\n"; // 输出: Addition: 8
echo "Subtraction: " . $calculator->subtract(5, 3) . "\n"; // 输出: Subtraction: 2

// 测试：验证计算器的功能是否正确
assert($calculator->add(5, 3) == 8);
assert($calculator->subtract(5, 3) == 2);

// 维护：如果有新的需求，比如乘法和除法，可以在Calculator类中添加相应的方法
class Calculator {
    public function add($a, $b) {
        return $a + $b;
    }

    public function subtract($a, $b) {
        return $a - $b;
    }

    public function multiply($a, $b) {
        return $a * $b;
    }

    public function divide($a, $b) {
        if ($b == 0) {
            throw new Exception("Division by zero");
        }
        return $a / $b;
    }
}

$calculator = new Calculator();
echo "Multiplication: " . $calculator->multiply(5, 3) . "\n"; // 输出: Multiplication: 15
echo "Division: " . $calculator->divide(5, 3) . "\n"; // 输出: Division: 1.6666666666667
?>