Php fpdf页面方向错误

我有fpdf页面方向的问题 . 我的部分代码：

$pdf=new PDF_MC_Table();
        $pdf->AliasNbPages();
        $pdf->AddPage('L','A3');
        $pdf->SetWidths(array(50,200,50,50,50));
        $pdf->SetFont('Arial','B',10);

        if(!empty($ow)){
                    $pdf->SetFont('Arial','B',10);
                    $pdf->Ln();
                    $pdf->Cell('50',7,'OPEN TASK OVERDUE');
                    $pdf->SetFont('Arial','',10);
                    $groupedTasks=[];
                    foreach ($ow as $w) {
                        $groupedTasks[$w['date_due']][] =$w;
                    }
                    foreach ($groupedTasks as $key=>$val) {
                        $pdf->SetFont('Arial', 'B', 10);
                        $pdf->SetFillColor(0,0,0);
                        $pdf->SetTextColor(255,255,255);
                        $pdf->Ln();
                        $pdf->Cell('50',6,$key." (Due Date)",'','','',true);$pdf->Ln();
                        $pdf->Ln();
                        $pdf->SetFillColor(255,255,255);
                        $pdf->SetTextColor(0,0,0);
                        $pdf->Cell(50,7,"Lead",1,0,'C',true);
                        $pdf->Cell(200,7,"Note",1,0,'C',true);
                        $pdf->Cell(50,7,"Task type",1,0,'C',true);
                        $pdf->Cell(50,7,"Due date",1,0,'C',true);
                        $pdf->Cell(50,7,"Assign to",1,0,'C',true);
                        $pdf->Ln();
                        $pdf->SetFont('Arial', '', 10);
                        foreach ($val as $value) {
                            $pdf->Row([iconv('UTF-8', 'windows-1252', $value['lead_name']),
                                    iconv('UTF-8', 'windows-1252', $value['content']),
                                    iconv('UTF-8', 'windows-1252', $value['task_type']),
                                    iconv('UTF-8', 'windows-1252', $value['date_due']),
                                    iconv('UTF-8', 'windows-1252', $value['assign_to'])]
                            );
                        }
                    }

                }

我的问题是，某些页面（3-4）处于A3方向，A4中的其他设置方向和我的表格被打破 . 可能有什么问题？我设定了方向如： $pdf->AddPage('L','A3');

我的屏幕：http://clip2net.com/s/3KetEPv

希望你能帮帮我 . 谢谢！