如果下面白色部分中的表单被提交，您如何在welcome.php 中输出 "first name" 字段中的值？
Hint: The http method is not the same as in Exercise 1.
<form action="welcome.php" method="post">
First name: <input type="text" name="fname">
</form>
<html>
<body>
Welcome <?php echo @(15); ?>
</body>
</html>
<form action="welcome.php" method="post">
First name: <input type="text" name="fname">
</form>
<html>
<body>
Welcome <?php echo $_POST["fname"]; ?>
</body>
</html>
<form action="welcome.php" method="post">
First name: <input type="text" name="fname">
</form>
<html>
<body>
Welcome <?php echo $_POST['fname']; ?>
</body>
</html>