Converting language name to locale code

Define :

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",
    "sn" => "Shona",
    "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, $languageCodes);
}

Then you just call:

echo getLocaleCodeForDisplayLanguage("French");

and it will return fr

I found the list of the ISO 639-1 codes on this site.

You can do this by PHP intl extension (available on PHP 5.3.2+).

<?php

if (version_compare(PHP_VERSION, '5.3.2', '<=')) {
    exit ('php_intl extension is available on PHP 5.3.2 or later.');
}    
if (!class_exists('Locale')) {
    exit ('You need to install php_intl extension.');
}

function getLocaleByDisplayName($displayName, $localeToSearch = 'en') {
    // get all available locales
    $allLocales = ResourceBundle::getLocales('');
    //var_dump($allLocales);

    $foundLocales = [];
    foreach ($allLocales as $locale) {
        $currentName = Locale::getDisplayLanguage($locale, $localeToSearch);
        if (strncmp($currentName, $displayName, strlen($currentName)) === 0) {
            $foundLocales[] = $locale;
        }
    }
    return $foundLocales;
}

$locales = getLocaleByDisplayName('Japanese', 'en');
var_dump($locales);
/*
array(2) {
[0]=>
string(2) "ja"
[1]=>
string(5) "ja_JP"
}
*/

$locales = getLocaleByDisplayName('スワヒリ語', 'ja');
var_dump($locales);
/*
array(5) {
[0]=>
string(2) "sw"
[1]=>
string(5) "sw_CD"
[2]=>
string(5) "sw_KE"
[3]=>
string(5) "sw_TZ"
[4]=>
string(5) "sw_UG"
}
*/

There could be multiple locales pointing the same language name, if you need to get only one, you may have to search the shortest locale or something.

You can use thephpleague/iso3166 package by php league which implemented ISO 3166-1 data. For example, you can use:

$data = (new League\ISO3166\ISO3166)->name('Netherlands');
$data = (new League\ISO3166\ISO3166)->alpha2('NL');
$data = (new League\ISO3166\ISO3166)->alpha3('NLD');
$data = (new League\ISO3166\ISO3166)->numeric('528');
/*
result is:
[
    'name' => 'Netherlands',
    'alpha2' => 'NL',
    'alpha3' => 'NLD',
    'numeric' => '528',
    'currency' => [
        'EUR',
    ]
]
*/