I am including the same "random.inc" in foo.php and bar.php. For each, I want reproducible "random" results.
So in foo.php I always want one set of numbers and/or keywords. In bar.php another. Which shouldn't change on reload. That's what I mean by contant pseudo-random. And that's why I seeding on the url. However I still get different results for individual numbers as well as for array pickson every reload. This is the full php file:
<?
header('Content-Type: text/plain');
$seed = crc32( $_SERVER['REQUEST_URI'] );
echo "phpversion: ".phpversion()."\nseed: $seed\n";
srand( $seed ); // (seed verified to be contant as expected)
// neither single values nor array pics turn out deterministic
echo ''.rand(0,100).' '.rand(0,100).' '.rand(0,100)."\n";
$values = array( '0'=>21,'1'=>89,'2'=>96,'3'=>47,'4'=>88 );
print_r( array_rand( $values, 3 ) );
?>
In the days of PHP4.1 it was (verified) possible to achieve constant pseudo-random like this. array_rand API documentation describes as a feature that since 4.2 initialization happens automatically. Perhaps this is overriding any explicit seeding? (if so, perhaps explicit seeding should raise an internal PHP flag, preventing automatic seeding?). Btw: mt_srand() and srand() are equally not working.
I would really like to get my deterministic / constant pseudo-random back...
Update: Solution below (Windows and/or version 5.2 's fault)
Works for me (PHP/5.3.6):
<?php
$data = range(1, 100);
srand(1);
print_r(array_rand($data, 3));
... always prints:
Array
(
[0] => 21
[1] => 89
[2] => 95
)
... in my machine. Apparently, the exact numbers differ depending on the exact environment but they're reproducible.
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