Is this an acceptable PHP connection class?

Is this an acceptable PHP connection class?

I've recently been trying to come up with an easy to use connection class.
The following implementation connects, queries and returns results and a
count.
Am I on the right track? Or does this go against standards completely? I'm
trying to stay away from the requirement to instantiate the class, so I'm
using a static method initially and returning a query object that can
fully chain.
class DB {
protected static $_connection = null;
public static function connect() {
if(!self::$_connection) {
try {
$pdo = new PDO('mysql:host=localhost;dbname=database', 'root',
'');
} catch(PDOException $e) {
die($e->getMessage());
}
self::$_connection = $pdo;
}
}
public static function query($sql) {
self::connect();
return new Query($sql);
}
}
class Query extends DB {
protected $_pdo = null,
$_query = null,
$_results = null,
$_count = null;
public function __construct($sql) {
$this->_pdo = self::$_connection;
$this->_query = $this->_pdo->prepare($sql);
if($this->_query->execute()) {
$this->_results = $this->_query->fetchAll(PDO::FETCH_OBJ);
$this->_count = $this->_query->rowCount();
return $this;
} else {
die('Query failed');
}
}
public function results() {
return $this->_results;
}
public function count() {
return $this->_count;
}
}
And the usage:
$users = DB::query('SELECT * FROM users LIMIT 10');
if(!$users->count()) {
echo 'Sorry, no results.';
} else {
foreach($users->results() as $user) {
echo $user->username, '<br>';
}
}