PHP を使用して簡単な電卓関数を実装する方法

<form method="post">
  <input type="text" name="num1" placeholder="请输入第一个数字" required>
  <select name="operator">
    <option value="+">+</option>
    <option value="-">-</option>
    <option value="*">*</option>
    <option value="/">/</option>
  </select>
  <input type="text" name="num2" placeholder="请输入第二个数字" required>
  <button type="submit">计算</button>
</form>

if ($_SERVER['REQUEST_METHOD'] === 'POST') {
  $num1 = $_POST['num1'];
  $num2 = $_POST['num2'];
  $operator = $_POST['operator'];

  if (!is_numeric($num1) || !is_numeric($num2)) {
    echo "请输入有效数字！";
  } else {
    switch ($operator) {
      case '+':
        $result = $num1 + $num2;
        break;
      case '-':
        $result = $num1 - $num2;
        break;
      case '*':
        $result = $num1 * $num2;
        break;
      case '/':
        if ($num2 == 0) {
          echo "除数不能为0！";
        } else {
          $result = $num1 / $num2;
        }
        break;
      default:
        echo "请选择有效运算符！";
    }

    echo "计算结果：$result";
  }
}