I have a PHP query in my website which detects if the user is on a desktop and displays a part of the header (and therefore leaves out the header on mobile, which is what it's intended to do).
It was working perfectly but now I've started using Page Caching, when I visit the site on mobile, the part of the header is now showing, due to the cache.
Is there a way I can exclude this PHP query from being cached at all please? It's in my header.php.
The website is http://www.bitofageek.com if you need to look. Thanks.
