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Bug #40187 mt_rand(), rand()
Submitted: 2007-01-21 19:06 UTC Modified: 2007-01-21 19:18 UTC
From: callawey at gmail dot com Assigned:
Status: Not a bug Package: Math related
PHP Version: 5.2.0 OS: windows xp
Private report: No CVE-ID: None
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 [2007-01-21 19:06 UTC] callawey at gmail dot com 
Description:
------------
rand and mt_rand generates random lenght integer between -9999999999 and +9999999999. 

example mt_rand(100000000000, 999999999999);
outputs: -564, -688852, 5586666988, -68889558

Reproduce code:
---------------
$str = mt_rand(100000000000, 999999999999);

Expected result:
----------------
positive numbers between 100000000000 and 999999999999

Actual result:
--------------
-492911349,1162038978,-219333642

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 [2007-01-21 19:10 UTC] iliaa@php.net 
Thank you for taking the time to write to us, but this is not
a bug. Please double-check the documentation available at
http://www.php.net/manual/ and the instructions on how to report
a bug at http://bugs.php.net/how-to-report.php

Integer overflow on 32 bit systems is the cause.
 [2007-01-21 19:12 UTC] callawey at gmail dot com 
while($row = $DB->fetchArray($result))
		{
			for($i=0;$i<=12;$i++)
			{
				$str .= rand(0,9);
			}
			//$str = mt_rand(100000000000, 999999999999);  
			
			$sqlc = sprintf("UPDATE %s SET user_id='%s' WHERE id='%s'", $DB->prefix("users"), $str, $row["id"]);
			$DB->queryF($sqlc);
		}



this code makes all colums -1
 [2007-01-21 19:18 UTC] callawey at gmail dot com 
while($row = $DB->fetchArray($result))
		{
			$str = "";
			for($i=0;$i<=12;$i++)
			{
				$str .= rand(0,9);
			}
			
			$sqlc = sprintf("UPDATE %s SET user_id='%s' WHERE id='%s'", $DB->prefix("users"), $str, $row["id"]);
			$DB->queryF($sqlc);
		}

this returns same number everytime even i use $str = ""; in every loop Why ?
 
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