What potential language compatibility issues should be considered when developing a PHP application that relies on browser language settings?

When developing a PHP application that relies on browser language settings, potential language compatibility issues to consider include ensuring that the application can properly handle different languages and character encodings, providing translations for different languages, and formatting dates, numbers, and currencies based on the user's language settings. One way to solve these issues is to use PHP's built-in functions for handling multilingual content and internationalization, such as `setlocale()` and `strftime()`.

// Set the locale based on the user's browser language settings
$locale = $_SERVER['HTTP_ACCEPT_LANGUAGE'];
setlocale(LC_ALL, $locale);

// Format a date based on the user's language settings
$date = strftime('%A, %B %d, %Y', strtotime('today'));

// Output the formatted date
echo $date;