Note: for more than 1 reroll, the number in the client seed will be changed to match each subsequent reroll.

<?php

$client_seed = 'Lucky ID reroll 1';
$server_seed = 'chatgame server seed';

$result_seed = hash_hmac('sha512', $server_seed, $client_seed);
$result_number = hexdec(substr($result_seed,0,10));
$lucky_number = abs($result_number % 1000);

echo $lucky_number;