Pass variable to TCPDF class header or any class function

class MYPDF extends TCPDF {
    public $template;
     
    public function setData($template){
    $this->template = $template;
    }
    public function Header() {
        // get the current page break margin
        $bMargin = $this->getBreakMargin();
        // get current auto-page-break mode
        $auto_page_break = $this->AutoPageBreak;
        // disable auto-page-break
        $this->SetAutoPageBreak(false, 0);
        // set bacground image
        $img_file = 'uploads/template_background_image/'.$this->template.'.png';
        $this->Image($img_file,0, 100, 390, 397, '', '', '', false, 300, '', false, false, 0);
        // restore auto-page-break status
        $this->SetAutoPageBreak($auto_page_break, $bMargin);
        // set the starting point for the page content
        
        
    }
    }
 
 
$pdf = new MYPDF(PDF_PAGE_ORIENTATION, PDF_UNIT, array(400,500), true, 'UTF-8', false);
$pdf->setData($template);