Echo不工作？

I'm trying to do a simple PHP script that can get a name from the URL and then print a "hello" message for that name. The variable I'm after is displayed as fname in the URL as I intend to add a middle and last name later on. I believe I've done the get correctly, but when I enter the first name and submit, I'm lead to just a blank screen.

<html>
 <head>
  <title>PHP Test</title>
 </head>
 <body>
<?php echo 'Hello ' . htmlspecialchars($_GET["fname"]); ?>
 </body>
</html>

And here is the HTML page where this PHP script is called.

<!DOCTYPE html>
<html>
    <head>
        <title>Hello World</title>
        <meta charset="utf-8">

    </head>
    <body>
    <form action="helloWorld.php" method="get">
        <h2>Name Form</h2>
        <table border="0">
           <tr>
              <td>First Name:</td>
              <td><input type="text" name="fname" id="fname"></td>
           </tr>
           <tr>
              <td>Middle Name:</td>
              <td><input type="text" name="mname" id="mname"></td>
           </tr>
           <tr>
              <td>Last Name:</td>
              <td><input type="text" name="lname" id="lname"></td>
           </tr>
        </table>
        <input type="submit" name="btnSubmit" id="btnSubmit"        value="Submit">&nbsp;&nbsp;&nbsp;&nbsp;
        <input type="reset" name="btnReset" id="btnReset" value="Reset Form">
        </form>

    </body>
</html>

</div>