theme.php
<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<?=$lia->getHeadHtml()?>
</head>
<body>
<?=$lia->view('theme/Header');?>
<main>
<?=$content?>
</main>
<?=$lia->view('theme/Footer');?>
</body>
</html>