pagina.php

<?php
$d = new DateTime();
?>
<section class="content-header" style="padding-top: 0px;">
  <center>
    <h1>
      Comprobante de Compra
    </h1>
  </center>
</section>
<!-- Main content -->
<section class="content">
  <div class="row" style="margin-left:10%;">
    <iframe src="respaldo/" width="90%" frameborder="0" height="800">
      <p>Your browser does not support iframes.</p>
    </iframe>
  </div>
</section>

respaldoController.php

<?php

class RespaldosController{
	
		public function __construct() {
			if (($_SESSION['id_emp']) == "") {
				header("Location: ".Conectar::ruta()."?controller=login");
			}
		}
		public function index() {
      require_once("views/layout/template.php");
			require_once("views/respaldo/pagina.php");
		}
	}
	?>