Unfortunately, you don't say where the error is occurring.
(Incidentally, PHP follows most languages by indexing arrays starting from 0 rather than 1).
$TopicList->MoveFirst;
Is that supposed to be a property lookup or a method call. The name makes it look like the latter, but then it should have been written $TopicList->MoveFirst().
Similarly,
$GetSeat->Fields["SeatNumber"]->$Value
is "Value" supposed to be a property of that Fields array (in which case it should have been written $GetSeat->Fields["SeatNumber"]->Value)? If not, where does the variable $Value get its value from?