PHP - Tiempo trascurrido entre 2 horas

<TABLE id='table'>

<TR>

    <TH>ID.No</TH>

    <TH>Nombre</TH>

    <TH>Numero de Cedula</TH>

    <TH>Fecha</TH>

    <TH>Hora Entrada</TH>

    <TH>Hora Salida</TH>

    <TH>Tiempo Trascurrido</TH>

</TR>

<?php

session_start();

//Connect to database

require'connectDB.php';

$seldate = $_SESSION["exportdata"];

$sql = "SELECT * FROM logs WHERE DateLog='$seldate' ORDER BY id DESC";

$result=mysqli_query($conn,$sql);

if (mysqli_num_rows($result) > 0)

{

  while ($row = mysqli_fetch_assoc($result))

  {

?>

        <TR>

        <TD><?php echo $row['id'];?></TD>

        <TD><?php echo $row['Name'];?></TD>

        <TD><?php echo $row['SerialNumber'];?></TD>

        <TD><?php echo $row['DateLog'];?></TD>

        <TD><?php echo $row['TimeIn'];?></TD>

        <TD><?php echo $row['TimeOut'];?></TD>

        <TD><?php

        //Aquí necesito ingresar la diferencia entre TimeIn y Time Out

        ?></TD>

        </TR>

<?php

  }

}

?>

</TABLE>

echo date("H:m:s", strtotime($row['TimeOut'])-strtotime($row['TimeIn']));

$dateIn = new DateTime('2019-09-16 19:51:26');

$dateOut = (clone $dateIn)->setTime(21, 49, 14);

$difference = ($dateIn->diff($dateOut))->format('%H:%I:%S'); // "01:57:48"

<TD><?php

    $Hora1=new DateTime($row['TimeIn']);

    $Hora2=new DateTime($row['TimeOut']);

    $dateInterval = $Hora1->diff($Hora2);

    echo $dateInterval->format('%H horas %i minutos %s segundos').PHP_EOL;

?></TD>