AliasNbPages

class PDF extends FPDF
{
function Footer()
{
    // Go to 1.5 cm from bottom
    $this->SetY(-15);
    // Select Arial italic 8
    $this->SetFont('Arial','I',8);
    // Print current and total page numbers
    $this->Cell(0,10,'Page '.$this->PageNo().'/{nb}',0,0,'C');
}
}

$pdf = new PDF();
$pdf->AliasNbPages();