Get referer with IE7/IE8

I develop a plugin where I need to get the referer of a page when this page loads.

I call wp_get_referer(); in an action on wp_footer.

My code does not work in MS IE 7+, although it works in all other browsers, including MS Edge.

You can check here
click on the US or UK flag at the bottom of the page.
On the new page which is displayed, I echo the referer at the bottom of the page.
The referrer is displayed in all browsers except MS IE7+ (I use MS IE 11).

If I put PHP pages which are not WP pages, I can get the referer even on MS IE 7+.

You can check here
click on 'cliquer ici'
The referrer is well displayed using $_SERVER["HTTP_REFERER"].

I also tried to use $_SERVER["HTTP_REFERER"] in my plugin but that did not solve the problem.

Please advise.