PDO as constructor argument

I have the following class:

class UserRepository {

    private $conn;

    public function __construct($conn) {
        $this->$conn = $conn;
    }

    //Methods omitted

}

I use the following to create a UserRepository object:

$conn = new PDO("mysql:host=".DB_SERVER.";dbname=".DB_DATABASE, DB_USERNAME, DB_PASSWORD);
$userRepository = new UserRepository($conn);

I’m getting the following error in the constructor of the UserRepository:

Recoverable fatal error: Object of class PDO could not be converted to string

What am I doing wrong?

Answer

Your constructor uses the variable as dynamic attribute-name. Therefore it tries to convert it to a string. $this->{$conn} = $conn vs. $this->conn = $conn.

    public function __construct($conn) {
        $this->conn = $conn;
    }