สอบถาม TCPDF เวลาขึ้นหน้าใหม่จะให้โหลด background image ทุกครั้ง

 if(isset($_POST["create_pdf"]))  
 {  
      require_once('tcpdf/tcpdf.php');  
      $obj_pdf = new TCPDF('P', PDF_UNIT, PDF_PAGE_FORMAT, true, 'UTF-8', false);  
      $obj_pdf->SetCreator(PDF_CREATOR);  
      $obj_pdf->SetTitle("Export HTML Table data to PDF using TCPDF in PHP");  
      $obj_pdf->SetHeaderData('', '', PDF_HEADER_TITLE, PDF_HEADER_STRING);  
      $obj_pdf->setHeaderFont(Array(PDF_FONT_NAME_MAIN, '', PDF_FONT_SIZE_MAIN));  
      $obj_pdf->setFooterFont(Array(PDF_FONT_NAME_DATA, '', PDF_FONT_SIZE_DATA));  
      $obj_pdf->SetDefaultMonospacedFont('helvetica');  
      $obj_pdf->SetFooterMargin(PDF_MARGIN_FOOTER);  
      $obj_pdf->SetMargins(PDF_MARGIN_LEFT, '5', PDF_MARGIN_RIGHT);  
      $obj_pdf->setPrintHeader(false);  
      $obj_pdf->setPrintFooter(false);  
      $obj_pdf->SetAutoPageBreak(TRUE, 10);  
      $obj_pdf->SetFont('helvetica', '', 12);  
      $obj_pdf->AddPage('P', 'A4');  
      $content = '<style>
body  {
  background-image: url("Catalog.jpg");
}
</style>';  
      $content .= ' 
      <table>
               <tr>
        <th colspan="2"><b>You can also use Bootstraps grid system</b></th>
        <th colspan="2"><b>You can also use Bootstraps grid system</b></th>
      </tr>
      <tr>
      <td>You can also use Bootstraps grid system in conjunction with the .thumbnail class to create an image gallery.</td><td><img src="cinqueterre.jpg"  alt="Cinque Terre" width="100" height="100" align="left"></td>

       <td>You can also use Bootstraps grid system in conjunction with the .thumbnail class to create an image gallery.</td><td><img src="cinqueterre.jpg"  alt="Cinque Terre" width="100" height="100" align="left"></td>
      </tr>
      </table>  
      ';   
      $obj_pdf->writeHTML($content);  
      $obj_pdf->Output('sample.pdf', 'I');  
 }