php - Extending MySQLi

I've run into problems extending the MySQLi class. It won't let me add any properties.

class MySQLii extends MySQLi {

 public $database;


 public function MySQLii($host, $username, $password, $database){

  // Initialize MySQLi
  parent::MySQLi($host, $username, $password, $database);

  // Save database name
  $this->database = $database;

 }


}

$mysqlii = new MySQLii('localhost', 'root', 'password', 'database');

var_dump($mysqlii);

object(MySQLii)#1 (17) {
["affected_rows"]=> int(0)
["client_info"]=> string(48)

"mysqlnd 5.0.5-dev - 081106 -
$Revision: 289630 $"
["client_version"]=> int(50005)
["connect_errno"]=> int(0)
["connect_error"]=> NULL
["errno"]=> int(0) ["error"]=>
string(0) "" ["field_count"]=>
int(0) ["host_info"]=> string(42)
"MySQL host info: Localhost via UNIX
socket" ["info"]=> NULL
["insert_id"]=> int(0)
["server_info"]=> string(6) "5.1.44"
["server_version"]=> int(50144)
["sqlstate"]=> string(5) "00000"
["protocol_version"]=> int(10)
["thread_id"]=> int(4019)
["warning_count"]=> int(0) }

Note the absence of the database property I added in the MySQLii constructor. Am I missing something?