ID: 12455
Updated by: jflemer
Reported By: [EMAIL PROTECTED]
Old Status: Bogus
Status: Open
Bug Type: *Math Functions
Operating System: All
PHP Version: 4.0.4pl1, 4.0.6
New Comment:
OK, well can you check to see that microtime() is working for you? This script should
print out 100.
<?php
$a = array();
for($i=0; $i<100; $i++)
{
$a[((double)microtime()*1000000)]= 1;
}
echo count($a), "\n";
?>
BTW, your most recent example (calling a "remote" script) is essentially the same as
calling the local function pwd(). You still are re-seeding the PRNG with each time you
call the function. In order to produce a pseudo-random sequence you should only seed
the PRNG once. This is a hard thing to do in the case where you generate one random
number from the sequence per execution.
Here is something that works for me even though I call the srand() function inside the
function (though the randomness is probably pretty poor). You might be able to adapt
it in some way for your use. The idea here is that once you shuffle the array once,
you use that as the starting point for the next shuffle.
<?php
$pass_array =
array('a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z',0,1,2,4,5,6,7,8,9);
function pwd(&$pass_array) {
srand ((double)microtime()*1000000);
$password = '';
shuffle(&$pass_array);
for ($i=0; $i<6; $i++) { $password .= $pass_array[$i]; }
return $password;
}
$a = array();
for($i=0; $i<500; $i++) {
$a[pwd($pass_array)] = 1;
}
echo count($a), "\n";
This is not a *bug* (IMHO). This is a problem with your script, you might want to try
this discussion on [EMAIL PROTECTED] and see if people have more suggestions
for you.
Previous Comments:
------------------------------------------------------------------------
[2001-07-31 10:20:27] [EMAIL PROTECTED]
Ok, here's sample code that should wake you up. The problem
occurs even when srand is only called once / page load.
Create two PHP pages:
password.php
<?PHP
$password = "";
$array =
array('a','b','c','d','e','f','g','h','i','j','k','l','m','
n','o','p','q','r','s','t','u','v','w','x','y','z',0,1,2,4,
5,6,7,8,9);
srand ((double)microtime()*1000000);
shuffle(&$array);
for ($i=0; $i<6; $i++) { $password .= $array[$i]; }
echo $password;?>
load100times.php
<?PHP
$i=0;
while($i<100) {
$file = fopen ("http://localhost/password.php";, "r");
$password = fgets ($file, 128);
fclose($file);
$a[$password] = $password;
$i++;
}
echo "Count: " . count($a);
?>
Then load the load100times.php in your browser. The result
should be 100 but is still 4 on the machines I'm testing
on. I'm assuming srand is not ment to be run only once /
server start?
------------------------------------------------------------------------
[2001-07-31 10:00:28] [EMAIL PROTECTED]
Try moving your srand() call outside of the pwd() function. That should fix it. The
posted script returns 4 for me on Solaris 5.8, and 500 when I move the srand() outside
of pwd().
srand() should only be called *once*.
Reopen this if that does not fix it.
------------------------------------------------------------------------
[2001-07-30 06:25:27] [EMAIL PROTECTED]
The same problem also occurs on PHP 4.0.6 on Darwin/PPC.
System info:
PHP Version 4.0.6
System: Darwin localhost 1.3.7 Darwin Kernel Version 1.3.7:
Sat Jun 9 11:12:48 PDT 2001;
root:xnu/xnu-124.13.obj~1/RELEASE_PPC Power Macintosh
powerpc
Configure Command './configure' '--with-mysql=/usr/local'
'--with-apxs=/usr/sbin/apxs' '--with-zlib=/usr'
Server API: Apache
Apache Version: Apache/1.3.20
------------------------------------------------------------------------
[2001-07-30 05:17:09] [EMAIL PROTECTED]
A friend tried to run the test code on his machine and also
got 4 as a result. This is a Linux machine so my original
guess of this being Solaris specific isn't true. The only
real common denominator seems to be the PHP version? I'm
trying to get an upgrade to see if this is happening under
4.0.6.
Here's more info on the two servers this is occuring on:
PHP Version: 4.0.4pl1
System:
Linux xxx.com 2.2.14 #2 SMP Tue Mar 14 14:42:34 PST 2000
i686 unknown
Configure Command: './configure'
'--with-apxs=/usr/local/apache/bin/apxs' '--with-xml'
'--with-mcrypt' '--with-mysql' '--enable-track-vars'
Server API: Apache
System: SunOS yyy.com 5.8 Generic_108528-02 sun4u sparc
SUNW,UltraSPARC-IIi-cEngine
Configure Command: './configure'
'--with-apache=../apache_1.3.14'
'--with-mysql=/usr/local/mysql' '--with-ldap=/usr/local'
'--with-db3=/usr/local/BerkeleyDB.3.2' '--with-gd=../gd1.5'
'--with-ttf=/usr/local' '--enable-wddx'
------------------------------------------------------------------------
[2001-07-29 16:41:51] [EMAIL PROTECTED]
Well, when I run that code I get 4, not 500. Upping the
number of iterations doesn't help. I think the problem is
with the particular build (extension/OS combination). Any
way to debug this?
------------------------------------------------------------------------
The remainder of the comments for this report are too long. To view
the rest of the comments, please view the bug report online at
http://bugs.php.net/?id=12455
Edit this bug report at http://bugs.php.net/?id=12455&edit=1
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