#43807 [Opn->Bgs]: array_rand doesn't return keys in random order
ID: 43807
Updated by: tony2001@php.net
Reported By: martin dot kober at wu-wien dot ac dot at
-Status: Open
+Status: Bogus
Bug Type: Arrays related
Operating System: Linux 2.6
PHP Version: 5.2.5
New Comment:
array_rand() uses the same algorithm as shuffle().
And I can't see any problems with both functions.
Previous Comments:
------------------------------------------------------------------------
[2008-01-10 17:55:39] martin dot kober at wu-wien dot ac dot at
Description:
------------
The keys that array_rand returns are uniformly distributed, but their
order is not:
Counting the 0, 1 and 2 of the sample code output, I consistently get
some distribution like this:
Overall count (this is fine):
0 1 2
649 694 657
Count per position (this is wrong):
0 1 2
[0] 500 181 319
[1] 149 513 338
0 is way too often in [0] (same for 1 in [1]), there must be some
problem with the algorithm.
Adding a shuffle() is a workaround, but this is a potential trap for
users depending on an even distribution.
There are some similar bugs in the DB, but they are all very old and
seem to be Windows-related.
Reproduce code:
---------------
for ($i = 1; $i <= 1000; $i++) {
echo implode(" ", array_rand(array(1,2,3), 2)), "<br>\n";
}
------------------------------------------------------------------------
--
Edit this bug report at http://bugs.php.net/?id=43807&edit=1
Thread (2 messages)