Get the user agent string of the user from a PHP file used to retrieve a CSS

Question

In an HTML page I have the following:

<link rel='stylesheet' href='retrievedCSS.php' type='text/css' media='all' />

Inside retrievedCSS.php, I request a CSS resource from a CDN and I return it to the client.

Problem is CDN is quite "dynamic", so that if I directly execute retrievedCSS.php using the address bar of a browser, I get a different resource based on its user-agent string.

However, in my case, it's the server requesting the resource to the CDN, not a client.

Apart from appending it as a parameter (retrievedCSS.php?ua=myUserAgent) from the HTML page, is there any other way I can get the user agent string of the user loading the HTML page in retrievedCSS.php?

Answer 1

When you're accessing a web page, your browser is adding the User-Agent to the request HTTP headers. As the CSS file is only another resource requested via HTTP, you should be able to access to header within the PHP file via:

$_SERVER['HTTP_USER_AGENT']

You can read about it in the PHP docs.

EDIT: That should even work for your dynamic CSS file, as the browser is adding the header to all of the HTTP requests.

Answer 2

get_browser() function. But it requires browscap.

Answer 3

You can access the user agent string using the variable $_SERVER['HTTP_USER_AGENT']