FPDF calls the user implemented Footer()
function like this :
// Page footer
$this->InFooter = true;
$this->Footer();
$this->InFooter = false;
You have defined the function like this :
function Footer($backToTOC) {
}
Which demands the caller to pass a variable. Thats why you get the "Missing argument" warning. You do not have to pass $backToTOC
since it (seems) to be defined already. Change the Footer function to
function Footer() {
global $backToTOC;
...
}
BTW, perhaps you also need to set the link / $backToTOC
to point at page 0.
$backToTOC = $pdf->AddLink();
$pdf->SetLink($backToTOC, -1, 0);