Description:
------------
A bias in the PHP 7.1 implementation of mt_rand() on 64-bit systems has been reported by Solar Designer on the mailing list. See https://externals.io/message/100229 for more information.

Test script:
---------------
<?php
mt_srand(1234567890);
$total = 100000;
$max = 0x66666666;
$halves[0] = $halves[1] = 0;
for ($i = 0; $i < $total; $i++) {
    $halves[mt_rand(0, $max - 1) / ($max / 2)]++;
}
printf("%.1f%% vs. %.1f%%\n", 100. * $halves[0] / $total, 100. * $halves[1] / $total);
?>


Expected result:
----------------
50.0% vs. 50.0%

Actual result:
--------------
60.0% vs. 40.0%