提交表单时缺少字段

答案很简单:我没有指定name属性.

没有该name属性,浏览器就无法发送任何内容.所以这是我的工作形式:

<form action="form.php" method="post">
    <label for="firstName">First name: </label>
    <input type="text" id="firstName" name="firstName" />
    <label for="lastName">Last name: </label>
    <input type="text" id="lastName" name="lastName" />
    <label for="address">Address: </label>
    <input type="text" id="address" name="address" />
    <label for="age">Age: </label>
    <input type="text" id="age" name="age" />
    <button type="submit">Submit!</button>
</form>