function create_custom_directory($dir_name) {

    $upload_dir = wp_upload_dir(); // Get the uploads directory array

    $custom_dir = $upload_dir['basedir'] . '/' . $dir_name; // Specify the custom folder

    if (!file_exists($custom_dir)) {

        wp_mkdir_p($custom_dir);

        if(file_exists($custom_dir)) {

            return "Directory created successfully.";

        } else {

            return "Failed to create directory.";

        }

    } else {

        return "Directory already exists.";

    }

}

// Example usage

$dir_name = 'en';

echo create_custom_directory($dir_name);