Write(float h, string txt [, mixed link])
h
txt
link
// Begin with regular font
$pdf->SetFont('Arial', '', 14);
$pdf->Write(5, 'Visit ');
// Then put a blue underlined link
$pdf->SetTextColor(0, 0, 255);
$pdf->SetFont('', 'U');
$pdf->Write(5, 'www.fpdf.org', 'http://www.fpdf.org');