header.php

<?php

ob_start();

$httpHost = $_SERVER['HTTP_HOST'];
$requestUri = $_SERVER['REQUEST_URI'];
$queryString = $_SERVER['QUERY_STRING'];

$pathinfo = pathinfo($_ENV['SCRIPT_FILENAME']);
$extension = $pathinfo['extension'];

if ($extension != 'html') {
    header('Cache-Control: max-age=604800'); // 1 week
}

if ($extension == 'html') {
    header('Content-type: text/html; charset=utf-8');
}

if ($extension == 'css') {
    header('Content-type: text/css; charset=utf-8');
}

if ($extension == 'js') {
    header('Content-type: text/javascript; charset=utf-8');
}

if ($extension == 'png') {
    header('Content-type: image/png');
}

if ($extension == 'jpg') {
    header('Content-type: image/jpeg');
}

if ($extension == 'gif') {
    header('Content-type: image/gif');
}