在php中使用单选按钮的简单计算器

<form method="post" action="">
  <label for="num1">第一个数字：</label>
  <input type="number" name="num1" id="num1">
  
  <label for="num2">第二个数字：</label>
  <input type="number" name="num2" id="num2">
  
  <p>选择操作：</p>
  <label for="add">加法</label>
  <input type="radio" name="operation" value="add" id="add">
  
  <label for="subtract">减法</label>
  <input type="radio" name="operation" value="subtract" id="subtract">
  
  <label for="multiply">乘法</label>
  <input type="radio" name="operation" value="multiply" id="multiply">
  
  <label for="divide">除法</label>
  <input type="radio" name="operation" value="divide" id="divide">
  
  <input type="submit" value="计算">
</form>

<?php
if ($_SERVER['REQUEST_METHOD'] === 'POST') {
  $num1 = $_POST['num1'];
  $num2 = $_POST['num2'];
  $operation = $_POST['operation'];
  
  // 执行计算
  switch ($operation) {
    case 'add':
      $result = $num1 + $num2;
      break;
    case 'subtract':
      $result = $num1 - $num2;
      break;
    case 'multiply':
      $result = $num1 * $num2;
      break;
    case 'divide':
      $result = $num1 / $num2;
      break;
    default:
      $result = '未选择操作';
      break;
  }
  
  echo '计算结果：' . $result;
}
?>