You could have a look at rowCount() to see how many rows are returned.
Exactly what you asked for - all columns from your table for rows where the username and password match the supplied information.
Have a look at the variables, and what they contain. Use
var_dump() to see what’s in them.
Your query returns no rows.
Possibly a good thing to read more about PHP and then come back with any remaining questions. All of the above is in the documentation.
What is more concerning, though, is your query:
$stmt = $pdo->prepare('SELECT * FROM benutzer WHERE uname = ? AND pwd=?');
where you are providing the password into the query. This suggests you are either storing plain-text passwords (please, no) or you are using your own method of hashing / encrypting passwords. If you are doing either of these, please read up on
password_hash() for storing the password, and
password_verify() for checking it. Once you have implemented that, you can change the query to
$stmt = $pdo->prepare('SELECT * FROM benutzer WHERE uname');
and then use
password_verify() on the results.
And while you’re changing the query, consider changing it (and any others) to only retrieve the columns that you actually need. Selecting * all the time is a bit of a waste of resources.