Detect Browser Language in PHP

Question

I use the following PHP script as index for my website.

This script should include a specific page depending on the browser\'s language (automatically detected).

Answer 1

Unfortunately, none of the answers to this question takes into account some valid HTTP_ACCEPT_LANGUAGE such as:

• q=0.8,en-US;q=0.5,en;q=0.3: having the q priority value at first place.
• ZH-CN: old browsers that capitalise (wrongly) the whole langcode.
• *: that basically say "serve whatever language you have".

After a comprehensive test with thousands of different Accept-Languages in my server, I ended up having this language detection method:

define('SUPPORTED_LANGUAGES', ['en', 'es']);

function detect_language() {
    foreach (preg_split('/[;,]/', $_SERVER['HTTP_ACCEPT_LANGUAGE']) as $sub) {
        if (substr($sub, 0, 2) == 'q=') continue;
        if (strpos($sub, '-') !== false) $sub = explode('-', $sub)[0];
        if (in_array(strtolower($sub), SUPPORTED_LANGUAGES)) return $sub;
    }
    return 'en';
}