ctrlpanel/app/Http/Middleware/SetLocale.php

<?php

namespace App\Http\Middleware;

use Closure;
use Illuminate\Http\Request;
use Illuminate\Support\Facades\App;
use Illuminate\Support\Facades\Session;

class SetLocale
{
    function getLocaleCodeForDisplayLanguage($name){
        $languageCodes = array(
            "aa" => "Afar",
            "ab" => "Abkhazian",
            "ae" => "Avestan",
            "af" => "Afrikaans",
            "ak" => "Akan",
            "am" => "Amharic",
            "an" => "Aragonese",
            "ar" => "Arabic",
            "as" => "Assamese",
            "av" => "Avaric",
            "ay" => "Aymara",
            "az" => "Azerbaijani",
            "ba" => "Bashkir",
            "be" => "Belarusian",
            "bg" => "Bulgarian",
            "bh" => "Bihari",
            "bi" => "Bislama",
            "bm" => "Bambara",
            "bn" => "Bengali",
            "bo" => "Tibetan",
            "br" => "Breton",
            "bs" => "Bosnian",
            "ca" => "Catalan",
            "ce" => "Chechen",
            "ch" => "Chamorro",
            "co" => "Corsican",
            "cr" => "Cree",
            "cs" => "Czech",
            "cu" => "Church Slavic",
            "cv" => "Chuvash",
            "cy" => "Welsh",
            "da" => "Danish",
            "de" => "German",
            "dv" => "Divehi",
            "dz" => "Dzongkha",
            "ee" => "Ewe",
            "el" => "Greek",
            "en" => "English",
            "eo" => "Esperanto",
            "es" => "Spanish",
            "et" => "Estonian",
            "eu" => "Basque",
            "fa" => "Persian",
            "ff" => "Fulah",
            "fi" => "Finnish",
            "fj" => "Fijian",
            "fo" => "Faroese",
            "fr" => "French",
            "fy" => "Western Frisian",
            "ga" => "Irish",
            "gd" => "Scottish Gaelic",
            "gl" => "Galician",
            "gn" => "Guarani",
            "gu" => "Gujarati",
            "gv" => "Manx",
            "ha" => "Hausa",
            "he" => "Hebrew",
            "hi" => "Hindi",
            "ho" => "Hiri Motu",
            "hr" => "Croatian",
            "ht" => "Haitian",
            "hu" => "Hungarian",
            "hy" => "Armenian",
            "hz" => "Herero",
            "ia" => "Interlingua (International Auxiliary Language Association)",
            "id" => "Indonesian",
            "ie" => "Interlingue",
            "ig" => "Igbo",
            "ii" => "Sichuan Yi",
            "ik" => "Inupiaq",
            "io" => "Ido",
            "is" => "Icelandic",
            "it" => "Italian",
            "iu" => "Inuktitut",
            "ja" => "Japanese",
            "jv" => "Javanese",
            "ka" => "Georgian",
            "kg" => "Kongo",
            "ki" => "Kikuyu",
            "kj" => "Kwanyama",
            "kk" => "Kazakh",
            "kl" => "Kalaallisut",
            "km" => "Khmer",
            "kn" => "Kannada",
            "ko" => "Korean",
            "kr" => "Kanuri",
            "ks" => "Kashmiri",
            "ku" => "Kurdish",
            "kv" => "Komi",
            "kw" => "Cornish",
            "ky" => "Kirghiz",
            "la" => "Latin",
            "lb" => "Luxembourgish",
            "lg" => "Ganda",
            "li" => "Limburgish",
            "ln" => "Lingala",
            "lo" => "Lao",
            "lt" => "Lithuanian",
            "lu" => "Luba-Katanga",
            "lv" => "Latvian",
            "mg" => "Malagasy",
            "mh" => "Marshallese",
            "mi" => "Maori",
            "mk" => "Macedonian",
            "ml" => "Malayalam",
            "mn" => "Mongolian",
            "mr" => "Marathi",
            "ms" => "Malay",
            "mt" => "Maltese",
            "my" => "Burmese",
            "na" => "Nauru",
            "nb" => "Norwegian Bokmal",
            "nd" => "North Ndebele",
            "ne" => "Nepali",
            "ng" => "Ndonga",
            "nl" => "Dutch",
            "nn" => "Norwegian Nynorsk",
            "no" => "Norwegian",
            "nr" => "South Ndebele",
            "nv" => "Navajo",
            "ny" => "Chichewa",
            "oc" => "Occitan",
            "oj" => "Ojibwa",
            "om" => "Oromo",
            "or" => "Oriya",
            "os" => "Ossetian",
            "pa" => "Panjabi",
            "pi" => "Pali",
            "pl" => "Polish",
            "ps" => "Pashto",
            "pt" => "Portuguese",
            "qu" => "Quechua",
            "rm" => "Raeto-Romance",
            "rn" => "Kirundi",
            "ro" => "Romanian",
            "ru" => "Russian",
            "rw" => "Kinyarwanda",
            "sa" => "Sanskrit",
            "sc" => "Sardinian",
            "sd" => "Sindhi",
            "se" => "Northern Sami",
            "sg" => "Sango",
            "si" => "Sinhala",
            "sk" => "Slovak",
            "sl" => "Slovenian",
            "sm" => "Samoan",
            "so" => "Somali",
            "sq" => "Albanian",
            "sr" => "Serbian",
            "ss" => "Swati",
            "st" => "Southern Sotho",
            "su" => "Sundanese",
            "sv" => "Swedish",
            "sw" => "Swahili",
            "ta" => "Tamil",
            "te" => "Telugu",
            "tg" => "Tajik",
            "th" => "Thai",
            "ti" => "Tigrinya",
            "tk" => "Turkmen",
            "tl" => "Tagalog",
            "tn" => "Tswana",
            "to" => "Tonga",
            "tr" => "Turkish",
            "ts" => "Tsonga",
            "tt" => "Tatar",
            "tw" => "Twi",
            "ty" => "Tahitian",
            "ug" => "Uighur",
            "uk" => "Ukrainian",
            "ur" => "Urdu",
            "uz" => "Uzbek",
            "ve" => "Venda",
            "vi" => "Vietnamese",
            "vo" => "Volapuk",
            "wa" => "Walloon",
            "wo" => "Wolof",
            "xh" => "Xhosa",
            "yi" => "Yiddish",
            "yo" => "Yoruba",
            "za" => "Zhuang",
            "zh" => "Chinese",
            "zu" => "Zulu"
        );
        return array_search($name, array_flip($languageCodes));
    }

    /**
     *
     * Handle an incoming request.
     *
     * @param Request $request
     * @param Closure $next
     * @return mixed
     */
    public function handle($request, Closure $next)
    {

            if (Session::has('locale')) {
                $locale = Session::get('locale', config('app.locale'));
            } else {
                if (!config('app.dynamic_locale')) {
                    $locale = config('app.locale');
                }else{
                    $locale = substr($request->server('HTTP_ACCEPT_LANGUAGE'), 0, 2);

                    if (!in_array($locale, config('app.available_locales'))
                        || in_array(strtolower($this->getLocaleCodeForDisplayLanguage($locale)), UNSUPPORTED_LANGS)) {
                        $locale = config('app.locale');
                    }

                }
            }
        App::setLocale($locale);

        return $next($request);
    }
}