WordPress - Load German Language Pack

<?php
function myPluginGetCurrentLanguageCode()
{
    $currentLanguage = null;

    $myPluginWPLANG = get_option('WPLANG', 'en_US');

    if (empty($myPluginWPLANG) || strlen($myPluginWPLANG) <= 1) {
        $myPluginWPLANG = 'en';
    }

    if (defined('ICL_LANGUAGE_CODE') || defined('POLYLANG_FILE')) {

        // Polylang
        if (function_exists('pll_current_language')) {

            $currentLanguage = pll_current_language();

            // If currentLanguage is still empty, we have to get the default language
            if (empty($currentLanguage)) {
                $currentLanguage = pll_default_language();
            }
        } else {
        // WPML
            $null = null;
            $currentLanguage = apply_filters('wpml_current_language', $null);
        }

        // Fallback
        if ($currentLanguage === 'all') {
            $currentLanguage = $myPluginWPLANG;
        }
    } else {
        $currentLanguage = $myPluginWPLANG;
    }

    return $currentLanguage;
}

load_plugin_textdomain('my-plugin', false, 'my-plugin/languages/');

// Load correct DE language file if any DE language was selected
if (in_array(myPluginGetCurrentLanguageCode(), ['de', 'de_DE', 'de_DE_formal', 'de_AT', 'de_CH', 'de_CH_informal'])) {
    // Load german language pack
    load_textdomain('my-plugin', 'full-path-to-your-plugin-folder/languages/my-plugin-de_DE.mo');
}