我使用这种方法来防止重复提交表单，到目前为止它在所有场合都有效。如果您需要其他问题，请告诉我，因为本教程假设您具有数据库和 PHP 的中级知识。
第 1 步：在您的数据库中添加一个字段，如下所示：
将 YOUR-TABLE 替换为数据库表的名称。
ALTER TABLE `YOUR-TABLE` ADD `token` VARCHAR(35) NULL DEFAULT NULL AFTER `creationtoken`, ADD UNIQUE (`token`) ;
在表单页面的第 2 步中，您将其添加到第一行：
它将创建一个唯一的令牌，该令牌将与您的查询一起插入到您的数据库表中，以便以后可以检查它以确保没有其他类似的令牌提交到您的数据库中，这意味着没有双重表单提交。
<?php
session_start();
date_default_timezone_set('America/Chicago');
$_SESSION['token'] = md5(session_id() . time());
?>
然后在提交按钮之前添加：
// add this before the submit button
// this will post the unique token to the processing page.
<div style="width:100%; color:#C00; font-weight:normal;">Session Token: <?php echo strtolower($_SESSION['token']) ?></div>
<input type="hidden" name="token" id="token" value="<?php echo $_SESSION['token']?>" />
// add this before the submit button
<input type="submit" id="submit" name="submit" class="button" value="Submit" />
第 3 步：现在在您的 process.php 页面上
//this is where all of your form processing takes place.
// this is where you call the database
// if you need the database file let me know...
include("../common/databaseclass.php");
$db= new database();
//here the token is posted then the database table is checked and
//if the form has already been added it will return a 1 and will
//cause the query to die and echo the error message.
$token = $_POST['token'];
$query = "SELECT token FROM YOURTABLE WHERE token = '$token' LIMIT 1";
$result = $db->query($query);
$num = mysql_num_rows($result);
if ($num>0) {die('your form has already been submitted, thank you');}
else {
$host = "localhost";
$user = "user";
$pass = "password";
$db_name = "database";
mysql_connect($host,$user,$pass);
@mysql_select_db($db_name) or die( "Unable to select database");
// table query
$sql1="INSERT INTO YOURTABLE (
`token`,
`user`,
`email`,
`password`,
`newaccount`,
`zipcode`,
`city`,
`state`,
`country`,
`telephone`,
`creationip`,
`createdaccount`
)
VALUES (
'$token',
'$username',
'$email',
'$password',
'$newaccount',
'$zipcode',
'$city',
'$state',
'$country',
'$phone',
'$ipadress',
'$createdaccount'
)";
$db->query($sql1);
header("location:" http://home.php ");
}