表单重新提交问题 PHP SQL

Question

如果我通过 PHP 向数据库中插入一条新记录，然后单击提交按钮，然后每次刷新页面时，它都会将最近添加的记录插入数据库中。我该如何阻止这种情况发生？我也不想在提交按钮之后重定向到另一个表单。奇怪的是，如果我单击提交按钮两次，然后刷新表单，它不会将重复项插入数据库。为什么是这样？请帮忙：/谢谢

代码如下：

<div class="insertDiv">
<form method="POST" action="contracts.php">
<?php
if(empty($_POST['ContractDate']) && empty($_POST['ComputerId2']) && empty($_POST['CustomerId'])  && empty($_POST['ContractLevel']))
{
}
else
{
include("dbinfo.inc.php");
$comm=@mysql_connect(localhost,$username,$password);
$rs=@mysql_select_db($database) or die( "Unable to select database"); 

$contractDate=$_POST['ContractDate'];
$computerID=$_POST['ComputerId'];
$customerID=$_POST['CustomerId'];
$contractLevel=$_POST['ContractLevel'];

$sql="INSERT INTO contract VALUES ('','$contractDate','$computerID', '$customerID', '$contractLevel')";
$result=mysql_query($sql)or die("Insert Error: ".mysql_error());
mysql_close();
}
?>

<div class = "myButton">
Insert
</div>

<p></p>
Enter contract start date:&nbsp
<input type="date" name="ContractDate" size=30 class="input"><br><br>
Enter computerID:&nbsp
<input type="text" name="ComputerId" size=30 class="input"><br><br>
Enter customerID:&nbsp
<input type="text" name="CustomerId" size=30 class="input"><br><br>
Enter contract level:&nbsp
<input type="text" name="ContractLevel" size=30 class="input"><br><br>
<input type="reset" value="Reset" class="button">&nbsp&nbsp&nbsp&nbsp
<input type="submit" value="Submit" class="button">
</form>
</div>

Answer 1

检查表格中已经存在的表格中的某些值，如果没有，则将数据插入表格中

或

1.生成一个随机字符串并将其存储在会话中，

2.然后将其作为隐藏值输出到您的表单中，

3.检查提交和存储变量，如果匹配处理您的请求，

4.转到 1.

Answer 2

只需使用会话确保表单仅提交一次即可。 这应该有效（我无法测试它）

<?php
// you should start the session before sending any output to the browser
session_start();
if($_SESSION['prevent'] && $_SESSION['prevent'] == $_POST['prevent'])$valid=true;
$_SESSION['prevent']=sha1(mt_rand(0,9999999));

?>
<div class="insertDiv">
<form method="POST" action="contracts.php">
<?php
if(empty($_POST['ContractDate']) && empty($_POST['ComputerId2']) && empty($_POST['CustomerId'])  && empty($_POST['ContractLevel']))
{
}
else
{

if($valid){

include("dbinfo.inc.php");
$comm=@mysql_connect(localhost,$username,$password);
$rs=@mysql_select_db($database) or die( "Unable to select database"); 

$contractDate=$_POST['ContractDate'];
$computerID=$_POST['ComputerId'];
$customerID=$_POST['CustomerId'];
$contractLevel=$_POST['ContractLevel'];

$sql="INSERT INTO contract VALUES ('','$contractDate','$computerID', '$customerID', '$contractLevel')";
$result=mysql_query($sql)or die("Insert Error: ".mysql_error());
mysql_close();
}
}
?>

<div class = "myButton">
Insert
</div>

<p></p>
Enter contract start date:&nbsp
<input type="date" name="ContractDate" size=30 class="input"><br><br>
Enter computerID:&nbsp
<input type="text" name="ComputerId" size=30 class="input"><br><br>
Enter customerID:&nbsp
<input type="text" name="CustomerId" size=30 class="input"><br><br>
Enter contract level:&nbsp
<input type="text" name="ContractLevel" size=30 class="input"><br><br>
<input type="reset" value="Reset" class="button">&nbsp&nbsp&nbsp&nbsp
<input type="hidden" value="<?php echo $_SESSION['prevent']; ?>">
<input type="submit" value="Submit" class="button">
</form>
</div>

Answer 3

阅读这篇文章，它将解释如何重定向，以便刷新不会重新提交表单。

http://en.wikipedia.org/wiki/Post/Redirect/Get