当php页面刷新时，浏览器会弹出一条消息给用户

可能重复：
避免在php页面上重新发送表单

Index.html

 <form method="post" action="demo.php">
             <input type="text" name="fname"/> 
             <input type="text" name="lname"/>
 </form>

demo.php

 <?php
       $firstname = $_POST['fname'];
       $lastname = $_POST['lname'];
       //some more php code to fill the webpage
  ?>

因此，用户输入他的名字和姓氏并提交表单，然后demo.php完成它的工作并正常工作，但当我按下F5或刷新demo.php时，下次我从浏览器中弹出

     // this message is from google chrome
     the page that you're looking used information that you entered.
     Returning to that page might cause any action to be repeated.
     Do you want to continute?
    // this message is from IE 7 or 8
    To display the webpage again,Internet Explorer needs to resend information
    you've previously submitted. If you were making a purchase, 
    you should click cancel to avoid duplicate transaction,else click retry.

为什么我会得到这个？我只想刷新页面。我不希望那个消息从浏览器中弹出。只需根据以前提交的值刷新页面，因为它会在我的数据库中创建重复的值。