PHP, Shorthand, If..Else using Ternary Operators

Question

Is there a oneliner for this? A nice Ternary OP?

$F_NAME = $_SESSION['USR']['F_NAME'];
if(isset($_POST['F_NAME'])) {$F_NAME = $_POST['F_NAME'];}

Basically "If the POST is sent, show that, even if the post is empty, otherwise grab the value from the session, but only if the post was not set or empty"

Really splitting hairs here...

looking for something like this:

$F_NAME = ? ($F_NAME ? isset($_POST['F_NAME']) : $_SESSION['USR']['F_NAME']);

Answer 1

Its supposed to be:

(conditions) ? true : false
   satisfies <--^      ^----> did not satisfy

So this equates into:

$F_NAME = isset($_POST['F_NAME']) ? $_POST['F_NAME'] : $_SESSION['USR']['F_NAME'];