How can language preference be detected and passed in the header for all browsers in PHP?

To detect and pass the language preference in the header for all browsers in PHP, you can use the `$_SERVER['HTTP_ACCEPT_LANGUAGE']` variable to retrieve the preferred language set by the user's browser. You can then use this information to set the appropriate language header in the response.

// Retrieve the preferred language from the user's browser
$language = substr($_SERVER['HTTP_ACCEPT_LANGUAGE'], 0, 2);

// Set the appropriate language header in the response
header('Content-Language: ' . $language);