Unexpected '$this' (T_VARIABLE)

<?php


class bd{

    private $hostname;
    private $dbname;
    private $username;
    private $password;
    private $option = array(
                                PDO::ATTR_PERSISTENT =>true ,
                                PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION
                             ); 


   protected $bdd;

   public function __construct()
   {
    $ini = parse_ini_file('Parameter/paraBD.ini')
    $this->$hostname = $ini['hostname'];
    $this->$dbname = $ini['databaseName'];
    $this->$username = $ini['username'];
    $this->$password = $ini['password'];
    connection();
   }

   public function connection()
   {
        $dsn = 'mysql:host='. $this->$hostname .';dbname='. $this->$dbname;
        $this->$bdd = new PDO($dsn, $this->$username, $this->$password, $this->$option);  
   }
}