You can just have those to HTML files created alread and put them in the same directory as the “main” file visitors load (the PHP file).
Then the php will check the current time and then depending on that it will include the right HTML.
<?
// Get the current hour of the day in 24 hour format (no leading zeros)
$hour = date("G");
if($hour >= 6 && $hour < 9) include("page1.html);
else if($hour >=9 && $hour < 11) include("page2.html");
else include("default.html");
?>