Go Premium for a chance to win a PS4. Enter to Win

x
?
Solved

Bug with session and md5?

Posted on 2002-03-03
4
Medium Priority
?
302 Views
Last Modified: 2010-05-18
Is there any known bug in md5-function?
Or is anything wrong with my session-function:

<?
  for ($i==0;$i<5000;$i++)
  {
    mt_srand((double)microtime()*1000000);
    $s =  str_replace(".","",$REMOTE_ADDR) + mt_rand(100000,999999);
    if ($s=="")
    {
      die ("s==0");
    }

    $xid = md5($s);
    if ($xid==0)
    {
      die("xid==0, s = $s");
    }
    else echo ("i=$i, s=$s, xid=$xid<p>");
  }

?>

The script does return xid==0 most of the times,
sometimes there are 2 valid md5-hash-values,
but never more than this.

One run as example:
----------
i=, s=887070, xid=1b38808a9dd9d678dcd154fdb063755e
i=1, s=524150, xid=53f52d26980bae606c37ce213ce34764
i=2, s=589563, xid=7a37ac718e05d27b25498e846a1c42b1
xid==0, s = 741154
-------

md5 should always return valid hash values, but not
xid==0, or am I wrong?

(tested with php version 4.06 and 4.1.1)

Thank you for help!

Gamba

0
Comment
Question by:Gamba
  • 2
  • 2
4 Comments
 
LVL 5

Accepted Solution

by:
andriv earned 400 total points
ID: 6837900
It is not a problem with the md5 it's with the condition of the if statement.  If you place echo $xid immediately after:

$xid = md5($s);

it will have a value every time.

But sometime for some reason it the condition:

($xid == 0) returns true. It's because the return value of md5() is datatype string and I beleive PHP at times converts it to a int (but because it's a string it's 0) for the sake of the condition to compare it to a number.

If you change it to

if($xid == "")

it will work like a charm.
0
 

Author Comment

by:Gamba
ID: 6837908
That's great!!
A small difference with great effect!

Now it works.

Thank you,

Gamba
0
 
LVL 5

Expert Comment

by:andriv
ID: 6838311
Glad I was able to help.
0
 

Author Comment

by:Gamba
ID: 6838596
I took a look at some older projects and found out,
that I always did the condition that way
and it worked fine . Do you maybe know, if this "sometimes handling as a number" is a inconsistency in a new version
of php (cause the only thing which changed, is that
we updated the php version to 4.1.1)?

Gamba
0

Featured Post

What does it mean to be "Always On"?

Is your cloud always on? With an Always On cloud you won't have to worry about downtime for maintenance or software application code updates, ensuring that your bottom line isn't affected.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

I imagine that there are some, like me, who require a way of getting currency exchange rates for implementation in web project from time to time, so I thought I would share a solution that I have developed for this purpose. It turns out that Yaho…
This article discusses four methods for overlaying images in a container on a web page
The viewer will learn how to create and use a small PHP class to apply a watermark to an image. This video shows the viewer the setup for the PHP watermark as well as important coding language. Continue to Part 2 to learn the core code used in creat…
This tutorial will teach you the core code needed to finalize the addition of a watermark to your image. The viewer will use a small PHP class to learn and create a watermark.
Suggested Courses

926 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question