PHP防止重复提交表单（helloweba网站经典实例）

 1 <?php
 2   session_start();
 3   header("Content-Type:text/html;charset:utf8");
 4   function set_token(){
 5       $_SESSION['token']=md5(microtime(true));
 6 
 7   }
 8   function valid_token(){
 9     $return=$_REQUEST['token']==$_SESSION['token']? true:false;
10      set_token();
11      return $return;
12   }
13   //如果token为空,则生成一个token
14   if(!isset($_SESSION['token'])||($_SESSION['token']=="")){
15       set_token();
16   }
17   if(isset($_POST['web'])){
18            if(!valid_token()){
19                      echo "请不要重复提交";
20            }else{
21                echo "提交成功,value:".$_POST['web'];
22            }
23 
24   }else{
25 ?>
26  <center>
27  <form method="post" action="">
28    <input type="hidden" name="token" value="<?php echo $_SESSION['token'] ?>" />
29    <input type="text"  class="input" name="web" value="www.baidu.com" />
30    <input type="submit"   class="btn"  value="提交" />
31  </form>
32 </center>
33 <?php 
34      } 
35 ?>