$queries = [
    'cars'=>'SELECT some FROM cars',
    'users'=>'SELECT some FROM users'
];

$results = [
    'cars'=>[],
    'users'=>[],
];

foreach($queries AS $name=>$query) {
    //тут выполнение запроса и далее как у Вас:
    while($row = mysql_fetch_array($result)) {
        $results[$name][] = $row;
    }
}