Solved

How to construct anti-refresh plugin?

Posted on 2009-07-08
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487 Views
Last Modified: 2012-06-21
We've got situation like this:
1. I'm entering page X,
2. then I click (or hold f5) for 20 seconds

What to do to avoid reloading page? (transfer and statistics)
Limit max pages download to 20 per minute?

Any solutions?
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Question by:AndyPSV
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Expert Comment

by:Ray Paseur
ID: 24806755
Not sure I understand your issue, but here is how I prevent multiple submissions of form data.
// PREVENT MULTIPLE SUBMISSIONS DUE TO DOUBLE CLICKS ON SUBMIT BUTTON
// EXAMPLE USAGE: 
// if ( multi_submit() ) 
// { /* error */ } 
// else 
// { /* normal processing */ }
// ASSUMES USE OF SESSIONS
 
function multi_submit($type = "post") 
{
 
// CHOOSE AND ENCODE THE REQUEST DATA
   $string = "";
   $input_array = ($type == "get") ? $_GET : $_POST;
   foreach ($input_array as $val) { $string .= $val; }
   $string = md5($string);
 
// SAME AS THE LAST REQUEST DATA?
   if ($_SESSION['_multi_submit'] === $string) 
   {
      return TRUE;
   } else 
   {
      $_SESSION['_multi_submit'] = $string;
      return FALSE;
   }
}

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Accepted Solution

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profya earned 500 total points
ID: 24807399
This code demonstrates how to control the number user refreshes a page. You can also use the microtime to control the span of time, however, because I am using windows I couldn't test this part.

create an include file, add the code attached to, then include the file created in your page.
Replace violate.htm with the page the script will redirect visitor to, when he/she exceeds refresh limits.
I hope you find it useful.
<?php
session_start();
$currentIp=$_SERVER['REMOTE_ADDR'];
if (isset($_SESSION['visitors']))
{
	$visitorsCache=$_SESSION['visitors'];
 
	if (isset($visitorsCache[$currentIp]))
	{
		$visitorsCache[$currentIp]->numberOfRefreshes++;
		$visitorsCache[$currentIp]->lastVisit=microtime(true);
	}
	else
	{
		$visitorsCache[$currentIp]=new visitorInfo();
		$visitorsCache[$currentIp]->numberOfRefreshes++;
		$visitorsCache[$currentIp]->lastVisit=microtime(true);
	}
	$datediff=(microtime(true)- $visitorsCache[$currentIp]->lastVisit);
	if ($visitorsCache[$currentIp]->numberOfRefreshes>5)
	{
		$visitorsCache[$currentIp]->numberOfRefreshes=0;
		header("location: violate.htm");
	}
}
else
{
	$visitors=array();
	if (isset($visitors[$currentIp]))
	{
		$visitors[$currentIp]->numberOfRefreshes++;
		$visitors[$currentIp]->lastVisit=microtime(true);
	}
	else
	{
		$visitors[$currentIp]=new visitorInfo();
		$visitors[$currentIp]->numberOfRefreshes++;
		$visitors[$currentIp]->lastVisit=microtime(true);
	}
	$_SESSION['visitors']=$visitors;
}
 
class visitorInfo
{
	public $numberOfRefreshes=0;
	public $lastVisit="";
}
?>

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Expert Comment

by:Ray Paseur
ID: 24808106
I guess you could also try some combination of ignore_user_abort() and sleep().  Can you please explain a little more about what you are trying to achieve?   Thanks, ~Ray
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Author Comment

by:AndyPSV
ID: 24808660
I just don't want to user make above 20 page refreshes in 1 minute
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LVL 14

Expert Comment

by:profya
ID: 24811514
Try my solution and change lines 19 and 20 to the following:
        $datediff=(microtime(true)- $visitorsCache[$currentIp]->lastVisit)*60;
        if ($visitorsCache[$currentIp]->numberOfRefreshes>20 && $datediff<1)

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Expert Comment

by:profya
ID: 24811536
Or adjust the values to suit your case, as I told you earlier, my machine uses Windows XP there for I can not test the elapsed time properly. I tested the solution as per refresh count, this represents 50% of the fix as I see.
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Author Comment

by:AndyPSV
ID: 24811690
how to transform this code - without class?
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Expert Comment

by:profya
ID: 24811769
The class helps you because many users will visit your website, each user with a specific ip will have its object. You can use arrays by the way to do that.
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LVL 110

Expert Comment

by:Ray Paseur
ID: 24814972
"I just don't want to user make above 20 page refreshes in 1 minute"

OK, I get that part.  Why not?
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Author Closing Comment

by:AndyPSV
ID: 31601256
thanks
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