lze to treba takto
<?php
header("Refresh: 20; url=\"$stranka\"");
// nebo
$refresh = 'Refresh: $cas; url="'.$stranka.'"';
header("$refresh");
?>
<!DOCTYPE HTML PUBLIC '-//W3C//DTD HTML 4.01//EN' 'http://www.w3.org/TR/html4/strict.dtd'>
<html>
<head>
...
....