Replaced stats variables with array

Variables $tanks, $helli, $air, $ship and $sol are replaced with $_stats, which is associative array with (key: string, value: integer), more specifically initiated like:
$this->_stats = array(
                   "tank" => 0,
                   "hellicopter" => 0,
                   "airplane" => 0,
                   "ship" => 0,
                   "soldier" => 0
                );