PHP Interface and Abstract Class best practice for inheritance?

When defining the structure and inheriting Interface and/or Abstract Class, which one is the best practice? And why? Here are 2 examples:

Here is the example for [Interface] -> [Abstract Class] -> [Class]

Interface DataInterface
{
    public function __construct($connection);
    public function connected();
    public function get();
}

Abstract class BaseData implements DataInterface
{
    protected $connection;

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


class UserData extends BaseData
{
    public function exists()
    {
        return is_connected($this->connection);
    }

    public function get()
    {
        return get_data($this->connection);
    }
}

$oUserData = new UserData(new Connection());

And here is the sample for [Abstract Class] -> [Class] without the Interface

Abstract class BaseData
{
    protected $connection;

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

    abstract public function connected();
    abstract public function get();
}

class UserData extends BaseData
{
    public function exists()
    {
        return is_connected($this->connection);
    }

    public function get()
    {
        return get_data($this->connection);
    }
}

$oUserData = new UserData(new Connection());

I am currently creating a small app (might grow larger) and confused on how to implement in the beginning correctly.

By the way, is this declaration for __construct() with parameter make sense in Interface?

public function __construct($connection);