PHP PDO Mysql

class dbConn {

   public $dsn;
   public $dbh;
   public $database;
   public $host;
   public $username;
   public $password;
   
   public function __constructor($host, $username, $password, $database) {	
          $this->host = $host;
          $this->database = $database;
          $this->username = $username;
          $this->password = $password;
      
	  $this->dsn = 'mysql:host='.$host.'dbname='.$database;  
	  self::connect();   
   }
   
   public function connect() {
   
      try {
	     $this->dbh = new PDO($dsn, $this->username, $this->password);
	     $this->dbh->setAttribute(PDO::ATTR_EMULATE_PREPARES, TRUE);
	     $this->dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
      } catch (PDOException $e) {
	     echo 'Erreur: ' . $e->getMessage();
	  }
   
   }
   
   public function getInstance() {
      return ($this->dbh);
   }
   
}

          $connexion = new dbConn('localhost', '***********','**********','******');
	  
	  $dbh = $connexion->getInstance();
	 	  
	  $sql = "SELECT * FROM *** WHERE email = :username AND password = :password LIMIT 1";	  
	  
	  
	  $stmt = $dbh->prepare($sql);
	  
	  $stmt->setFetchMode(PDO::FETCH_OBJ);
	  
	  $stmt->bindParam(':username', $this->username);
	  $stmt->bindParam(':password', $this->password);
	  $stmt->execute();
	  
	  $result = $stmt->fetchAll();
	  
	  foreach ($result as $row) {
	     echo $row->first_name . '  ' . $row->last_name; 
	  }