function generateRow(){
    $idviaje=$_REQUEST['idviaje'];
    $contents = '';
    $content = '';
    include_once('connection.php');

    $sql = "SELECT * FROM direccionescarga WHERE idviaje='$idviaje'";
    $query = $conn->query($sql);
    while($row = $query->fetch_assoc()){
        $content .= "
        <tr>
            <td colspan='2'>Remitente:".$row['nombredircar']."</td>
            <td colspan='3'>Dirección:".$row['direcciondircar']."</td>
        </tr>
        <tr>
            <th>Cod.Pos.".$row['codigopostaldircar']."</th>
            <th colspan='2'>Población".$row['poblaciondircar']."</th>
            <th>".$row['provinciadircar']."</th>
            <th>".$row['paisdircar']."</th>
        </tr>
        <tr>
            <th>".$row['fechacar']."</th>
            <th>".$row['horariocar']."</th>
            <th>".$row['referenciacar']."</th>
            <th>".$row['contactocar']."</th>
            <th>".$row['telefonocar']."</th>
        </tr>
        <tr>
            <td colspan='5'>".$row['observacionesdircar']."</td>

        </tr>
        ";
    }
    $contents=$content;


    return $contents;
}

<?php

    $idviaje=$_REQUEST['idviaje'];
    $username=$_REQUEST['username'];




        require_once('tcpdf/tcpdf.php');
        // Extend the TCPDF class to create custom Header and Footer
    class MYPDF extends TCPDF {



        // Page footer
        public function Footer() {
            // Position at 15 mm from bottom
            $this->SetY(-15);
            // Set font
            $this->SetFont('helvetica', 'I', 8);
            // Page number
            $this->Cell(0, 10, '´Página '.$this->getAliasNumPage().'/'.$this->getAliasNbPages(), 0, false, 'C', 0, '', 0, false, 'T', 'M');
        }
    }
        $pdf = new TCPDF('P', PDF_UNIT, PDF_PAGE_FORMAT, true, 'UTF-8', false);
        $pdf->SetCreator(PDF_CREATOR);
        $pdf->SetTitle("Generated PDF using TCPDF");
        $pdf->SetHeaderData('', '', PDF_HEADER_TITLE, PDF_HEADER_STRING);
        $pdf->setHeaderFont(Array(PDF_FONT_NAME_MAIN, '', PDF_FONT_SIZE_MAIN));
        $pdf->setFooterFont(Array(PDF_FONT_NAME_DATA, '', PDF_FONT_SIZE_DATA));
        $pdf->SetDefaultMonospacedFont('helvetica');
        $pdf->SetFooterMargin(PDF_MARGIN_FOOTER);
        $pdf->SetMargins(PDF_MARGIN_LEFT, '10', PDF_MARGIN_RIGHT);
        $pdf->setPrintHeader(false);
        $pdf->setPrintFooter(true);
        $pdf->SetAutoPageBreak(TRUE, 10);
        $pdf->SetFont('helvetica', '', 11);
        $pdf->AddPage();

        $tbl = <<<EOD
    <table cellspacing="0" cellpadding="1" border="1">
    <tr>
    <td>
    <table>
        <tr>
            <td><img src="images/logo_example.jpg" alt="test alt attribute" width="155" height="92" border="0"></td>
            <td><p sice="20"></p>
            <p></p>
            <p></p>
            <p></p>


            </td>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;


            <td><img src="images/logo_transnet.png" alt="test alt attribute" width="118" height="57" border="0" align="right"></td>
        </tr>
    </table>
    </td>
    </tr>
    </table>
    EOD;

    $pdf->writeHTML($tbl, true, false, false, false, '');

    $tbl2 = <<<EOD
    <table cellspacing="0" cellpadding="1" border="1">
        <tr>
            <td>Para:$idviaje</td>
            <td>De:$nombreuser</td>
        </tr>
    </table>
    EOD;

    $pdf->writeHTML($tbl2, true, false, false, false, '');

        function generateRow(){
            $idviaje=$_REQUEST['idviaje'];
            $contents = '';
            $content = '';
            include_once('connection.php');

            $sql = "SELECT * FROM direccionescarga WHERE idviaje='$idviaje'";
            $query = $conn->query($sql);
            while($row = $query->fetch_assoc()){
                $content .= "
                <tr>
                    <td colspan='2'>Remitente:".$row['nombredircar']."</td>
                    <td colspan='3'>Dirección:".$row['direcciondircar']."</td>
                </tr>
                <tr>
                    <th>Cod.Pos.".$row['codigopostaldircar']."</th>
                    <th colspan='2'>Población".$row['poblaciondircar']."</th>
                    <th>".$row['provinciadircar']."</th>
                    <th>".$row['paisdircar']."</th>
                </tr>
                <tr>
                    <th>".$row['fechacar']."</th>
                    <th>".$row['horariocar']."</th>
                    <th>".$row['referenciacar']."</th>
                    <th>".$row['contactocar']."</th>
                    <th>".$row['telefonocar']."</th>
                </tr>
                <tr>
                    <td colspan='5'>".$row['observacionesdircar']."</td>

                </tr>
                ";
            }
            $contents=$content;


            return $contents;
        }

        $content = '';
        $content .= '

            <table border="1" cellspacing="0" cellpadding="3">
               <tr>
                    <th width="100%" colspan="5">DIRECCIÓN DE CARGA</th>

               </tr>
          ';
        $content .= generateRow();
        $content .= '</table>';
        $pdf->writeHTML($content);





        $pdf->Output('members.pdf', 'I');


    ?>

function generateRow(){
            $idviaje=$_REQUEST['idviaje'];
            $contents = '';
            $content = '';
            include_once('connection.php');

            $sql = "SELECT * FROM direccionescarga WHERE idviaje='$idviaje'";
            $query = $conn->query($sql);
            while($row = $query->fetch_assoc()){
                $content .= '
                <tr>
                    <td colspan="2">Remitente:'.$row['nombredircar'].'</td>
                    <td colspan="3">Dirección:'.$row['direcciondircar'].'</td>
                </tr>
                <tr>
                    <th>Cod.Pos.'.$row['codigopostaldircar'].'</th>
                    <th>Población'.$row['poblaciondircar'].'</th>
                    <th>'.$row['provinciadircar'].'</th>
                    <th>'.$row['paisdircar'].'</th>
                </tr>
                <tr>
                    <th>'.$row['fechacar'].'</th>
                    <th>'.$row['horariocar'].'</th>
                    <th>'.$row['referenciacar'].'</th>
                    <th>'.$row['contactocar'].'</th>
                    <th>'.$row['telefonocar'].'</th>
                </tr>
                <tr>
                    <td colspan="5">'.$row['observacionesdircar'].'</td>

                </tr>

                ';
            }