How to navigate using the "Full version of the site" button on a mobile device?

Question

PHP

The site is fully responsive and adapts to the screen of mobile devices using the viewport. Now we need to enable users to see the Full version of the site using the button. How best to do this without the need to create another site specifically for mobile devices, separately for the desktop version. The site is made on Bitrix.

Answer 1

why, if the site is fully adaptive ?
And if you still need to, create a copy of the old css, remove all code related to adaptability (any media queries) and save it as desktop.css , and in the mobile version give a link by clicking on which the css file changes.
/?set_theme=desktop

if($_GET['set_theme'] == 'desktop'){
  //устанавливаете desktop.css и сохраняете в сессии
}

Answer 2

Most often they put a cookie (well, or another mark on the client), which determines whether to open a mobile phone or not