Using PHP code in HTML

Hi,

Yesterday only I bought your template for creating a photography site, I am using your Photography template. what I need it to add PHP code to photography.HTML file to be able to read all files in the directory and add them to the slider.
Like,
<?php
$dirname = "images/";
$images = scandir($dirname);
shuffle($images);
$ignore = Array(".", "..");
foreach($images as $curimg){
if(!in_array($curimg, $ignore)) {
echo "<li><a href='".$dirname.$curimg."'><img src='img.php?src=".$dirname.$curimg."&w=300&zc=1' alt='' /></a></li>\n";
}
}
?>

However, no matter where I add this in the HTML, at runtime the php code gets commented.

is it not possible to process PHP within the HTML file? Please help.

Same is the Case with js the script block doesn't get processed however, unlike PHP it doesn't get commented.

For php thing, it was my mistake index.php and index.html both were there and by default html was picked up, removing .html helped.

JS I still have to figure out as it works partially however, no error in the console, I will let you know in case I would need help.

Thanks