function get_hash_table($table, $userid)
{
$str = crc32($userid);

if ($str < 0) {
$hash = "0" . substr(abs($str), 0, 1);
} else {
$hash = substr($str, 0, 2);
}

return $table . "_" . $hash;
}

echo get_hash_table('message', 'user18991'); //结果为message_10
echo get_hash_table('message', 'user34523'); //结果为message_13