php采用session实现防止页面重复刷新，
php采用session实现防止页面重复刷新，
如何防止页面重复刷新，在php环境下可以利用session来轻松实现。
b.php的代码
<?php
//只能通过post方式访问
if ($_SERVER['REQUEST_METHOD'] == 'GET')
{header('HTTP/1.1 404 Not Found'); die('亲,页面不存在');}
session_start();
$fs1=$_POST['a'];
$fs2=$_POST['b'];
//防刷新时间,单位为秒
$allowTime = 30;
//读取访客ip，以便于针对ip限制刷新
/*获取真实ip开始*/
if ( ! function_exists('GetIP'))
{
function GetIP()
{
static $ip = NULL;
if ($ip !== NULL)
{
return $ip;
}
if (isset($_SERVER))
{
if (isset($_SERVER['HTTP_X_FORWARDED_FOR']))
{
$arr = explode(',', $_SERVER['HTTP_X_FORWARDED_FOR']);
/* 取X-Forwarded-For中第x个非unknown的有效IP字符? */
foreach ($arr as $xip)
{
$xip = trim($xip);
if ($xip != 'unknown')
{
$ip = $xip;
break;
}
}
}
elseif (isset($_SERVER['HTTP_CLIENT_IP']))
{
$ip = $_SERVER['HTTP_CLIENT_IP'];
}
else
{
if (isset($_SERVER['REMOTE_ADDR']))
{
$ip = $_SERVER['REMOTE_ADDR'];
}
else
{
$ip = '0.0.0.0';
}
}
}
else
{
if (getenv('HTTP_X_FORWARDED_FOR'))
{
$ip = getenv('HTTP_X_FORWARDED_FOR');
}
elseif (getenv('HTTP_CLIENT_IP'))
{
$ip = getenv('HTTP_CLIENT_IP');
}
else
{
$ip = getenv('REMOTE_ADDR');
}
}
preg_match("/[\d\.]{7,15}/", $ip, $onlineip);
$ip = ! empty($onlineip[0]) ? $onlineip[0] : '0.0.0.0';
return $ip;
}
}
/*获取真实ip结束*/
$reip = GetIP();
//相关参数md5加密
$allowT = md5($reip.$fs1.$fs2);
if(!isset($_SESSION[$allowT])){
$_SESSION[$allowT] = time();
}
else if(time() - $_SESSION[$allowT]-->$allowTime){
$_SESSION[$allowT] = time();
}
//如果刷新过快，则直接给出404header头以及提示
else {header('HTTP/1.1 404 Not Found'); die('来自'.$ip.'的亲,您刷新过快了');}
?>
代码很简单，无非是把ip，以及通过POST方式提交到需要防刷新页面的数据经过md5加密后写入session中，再通过存储的session来判断刷新时间间隔从而决定是否允许刷新。需要说明的是"$fs1=$_POST['a'];"、"$fs1=$_POST['a'];"两个参数是指其他页面通过post方式提交到需要防刷新页的参数。之所以除了ip之外还要加这些参数的原因是为了区别不同的post结果。（实际上所谓的防刷新也就是防止某一页面被反复提交。）
更具体的说，比如上述代码放在b.php页面的开头，我们在a.html页面有一个如下表单：
代码:
<!DOCTYPE> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>b.html</title> </head> <body> <form action="b.php" method="post" > <input type="hidden" id="a" name="a" value="a"/> <input type="hidden" id="b" name="b" value="b"/> <button name="" type="submit" >提交</button> </form> </body> </html>
可以看到这个页面提交的a和b 2个参数正是前面b.php中的2个参数（实际上应该反过来说，由提交页面的参数来决定)。在前面的php代码中，已经确定只能通过post访问被提交数据的页面，所以直接输入地址会得到一个404头的错误页面，只能通过post方式来得到页面，同时post刷新的时候会自己带上参数地址，这样就实现了同一页面每个ip的防止刷新效果。
另外我们可以在被post的页面增加通过referer判定来源网站，防止跨站提交，不过referer可以伪造，而且firefox和ie8经常莫名其妙出现referer丢失的情况，所以暂时也就不加这个代码。
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