Correct way to connect to sqlite db

Hello I am trying to connect to a sqlite db which is not in the folder where I am writing the pdo codes. Currently I have it something like this

$db = new PDO('sqlite:../daypilot.sqlite');

But this won't work, what will be the correct way to connect to the database for me. Also if the path to the db changes dynamically is there a way I could modify the pdo connection string? I mean could I use a variable to store the path of the database instead of using a hardcoded path?