I have the following warning notice from my functions.php file:

Warning: Use of undefined constant ENVIRONMENT - assumed 'ENVIRONMENT' (this will throw an Error in a future version of PHP)

This is the code in my functions.php:

$dist_dir = get_theme_root_uri() . "/" . wp_get_theme() . "/dist";

/* environement */
// Set your environment/url pairs
$environments = array(
    'local' => 'local.mysite.com',
    'staging' => 'staging.mysite.com',
    'production' => 'mysite.com'
);

// Get the hostname
$http_host = $_SERVER['HTTP_HOST'];
// Loop through $environments to see if there’s a match
foreach ($environments as $environment => $hostname) {
    //echo $hostname . " www";
    if (stripos($http_host, $hostname) !== false) {
        define('ENVIRONMENT', $environment);
        break;
    }
}

if (ENVIRONMENT == 'local') {
    define('ASSETSDIR', get_template_directory_uri() . '/assets');
} else {
    define('ASSETSDIR', $dist_dir . '/assets');
}

The line in relation with the notice is this one:

if (ENVIRONMENT == 'local') {

I’m not sure to understand why there is this warning notice and how to solve it.

Thank you.