From: webmaster at armondc dot com
Operating system: Windows 2000 Professional
PHP version: 4.3.4
PHP Bug Type: Unknown/Other Function
Bug description: rand() returns easily predictable numbers
Description:
------------
I'm not sure if this is a very major problem, or even a bug, but here
goes:
It seems rand() on Windows is very predictable.
I've tried it on 2 Windows Systems, and they were both predictable. It
showed a breif unpredictable segment, then followed by the same string of
characters over and over, and finally a few more unpredictable
characters.
I tried this on a FreeBSD 5.2 System, and it was unpreditable enough.
Seems to be a windows-only problem.
I also noticed bug#11108 - It seems similar, but the submitter was using
his own seeds, and I am using without.
Reproduce code:
---------------
<?php
// This will reproduce the problem
// on windows
for($x = 0; $x < 500; $x++) {
echo chr((rand()%32)+65);
}
// This is a quick-fix, but
// goes agaist the documentation's
// 'no need for srand()'
for($x = 0; $x < 500; $x++) {
srand(hexdec(substr(md5(microtime()), 0, 8)));
echo chr((rand()%32)+65);
}
?>
Expected result:
----------------
Something a bit random like:
HEOSITFS[ZYH_EVIVVXSLCWRHHC_]_L^PIBTC\TXPBWQLCM^VZSUUHOG[\VF[KCDGFZM^Q\IG^KAIYPIYBSBIMGHXIBMPHLY\OAZMYAZPJ_DF\X\QXR[GP]DQLRHMYIOERBMEKBDJMJPN]J\\KPES^EGRKKO^S[XL\SSHQXOYQU_JDMMZEUEOQOYMHJPYDTRRU_URHYJGXRQYDYADD]OBVUGC^GGSXPRJJAOAKRAYYN^Q\XFQJNOWQKAJBFONFXNDZFFIMYRLROH^]IM_MINJI\MJJAVG]_B_EAVC\O_\DHCHLX_NIOU^KMJF\K]VZDOZ_FAWCZC_IQK^[NTPZCC]XEFZ[\AG[PV^XLPRYVAS]ZPH^WAXYAZYGK_M_QKF]PRMP^BBPTRV^KV_VDOLFIM]WQNHVF^DYWGGSGLJ_ZMODG[Z_AAXBYD^FS\MITLZESC`DXLH]NWNIVWZZMVMSXFQMG[O[W[YSPVMTQLHD
Actual result:
--------------
An easily spotted pattern:
]F[LIBGHU^SDAZ_MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_MVK\
--
Edit bug report at http://bugs.php.net/?id=27052&edit=1
--
Try a CVS snapshot (php4): http://bugs.php.net/fix.php?id=27052&r=trysnapshot4
Try a CVS snapshot (php5): http://bugs.php.net/fix.php?id=27052&r=trysnapshot5
Fixed in CVS: http://bugs.php.net/fix.php?id=27052&r=fixedcvs
Fixed in release: http://bugs.php.net/fix.php?id=27052&r=alreadyfixed
Need backtrace: http://bugs.php.net/fix.php?id=27052&r=needtrace
Need Reproduce Script: http://bugs.php.net/fix.php?id=27052&r=needscript
Try newer version: http://bugs.php.net/fix.php?id=27052&r=oldversion
Not developer issue: http://bugs.php.net/fix.php?id=27052&r=support
Expected behavior: http://bugs.php.net/fix.php?id=27052&r=notwrong
Not enough info: http://bugs.php.net/fix.php?id=27052&r=notenoughinfo
Submitted twice: http://bugs.php.net/fix.php?id=27052&r=submittedtwice
register_globals: http://bugs.php.net/fix.php?id=27052&r=globals
PHP 3 support discontinued: http://bugs.php.net/fix.php?id=27052&r=php3
Daylight Savings: http://bugs.php.net/fix.php?id=27052&r=dst
IIS Stability: http://bugs.php.net/fix.php?id=27052&r=isapi
Install GNU Sed: http://bugs.php.net/fix.php?id=27052&r=gnused
Floating point limitations: http://bugs.php.net/fix.php?id=27052&r=float