Let's see if I can explain this and make sense at the same time... I've a website and a mobile app for that website. In some cases I'll use the view on the website in the app. I wont redirect the user to the website, but the website view will display in the application. But in this view I'll also make some changes. Lika media queries but at the same time not, because it the user is using a mobile but not the app, a the website will show as normal, but responsive of course.
UPDATE (trying to explain a bit better) If you use the mobile app, only a specific part of the website will be shown. In this case it will be product categories. Header, footer and all the other content will be gone except for the product categories. If you use the mobile and for example safari, the header, footer and all that stuff will be shown.
So the question here is how can I check, with using PHP, if the user is coming from a mobile app and thereafter display a certain view?