core-bundle/src/Resources/contao/library/Contao/System.php
public static function getLanguages($blnInstalledOnly=false)
	{
		$return = array();
		$languages = array();
		$arrAux = array();
		$langsNative = array();

		static::loadLanguageFile('languages');
		include __DIR__ . '/../../config/languages.php';

		foreach ($languages as $strKey=>$strName)
		{
			$arrAux[$strKey] = isset($GLOBALS['TL_LANG']['LNG'][$strKey]) ? Utf8::toAscii($GLOBALS['TL_LANG']['LNG'][$strKey]) : $strName;
		}

		asort($arrAux);

		$arrBackendLanguages = self::getContainer()->getParameter('contao.locales');

		foreach (array_keys($arrAux) as $strKey)
		{
			if ($blnInstalledOnly && !\in_array($strKey, $arrBackendLanguages))
			{
				continue;
			}

			$return[$strKey] = $GLOBALS['TL_LANG']['LNG'][$strKey] ?? $languages[$strKey];

			if (isset($langsNative[$strKey]) && $langsNative[$strKey] != $return[$strKey])
			{
				$return[$strKey] .= ' - ' . $langsNative[$strKey];
			}
		}

		// HOOK: add custom logic
		if (isset($GLOBALS['TL_HOOKS']['getLanguages']) && \is_array($GLOBALS['TL_HOOKS']['getLanguages']))
		{
			foreach ($GLOBALS['TL_HOOKS']['getLanguages'] as $callback)
			{
				static::importStatic($callback[0])->{$callback[1]}($return, $languages, $langsNative, $blnInstalledOnly);
			}
		}

		return $return;
	}
public static function getLanguages($blnInstalledOnly=false)
	{
		$return = array();
		$languages = array();
		$arrAux = array();
		$langsNative = array();

		static::loadLanguageFile('languages');
		include __DIR__ . '/../../config/languages.php';

		foreach ($languages as $strKey=>$strName)
		{
			$arrAux[$strKey] = isset($GLOBALS['TL_LANG']['LNG'][$strKey]) ? Utf8::toAscii($GLOBALS['TL_LANG']['LNG'][$strKey]) : $strName;
		}

		asort($arrAux);

		$arrBackendLanguages = self::getContainer()->getParameter('contao.locales');

		foreach (array_keys($arrAux) as $strKey)
		{
			if ($blnInstalledOnly && !\in_array($strKey, $arrBackendLanguages))
			{
				continue;
			}

			$return[$strKey] = $GLOBALS['TL_LANG']['LNG'][$strKey] ?? $languages[$strKey];

			if (isset($langsNative[$strKey]) && $langsNative[$strKey] != $return[$strKey])
			{
				$return[$strKey] .= ' - ' . $langsNative[$strKey];
			}
		}

		// HOOK: add custom logic
		if (isset($GLOBALS['TL_HOOKS']['getLanguages']) && \is_array($GLOBALS['TL_HOOKS']['getLanguages']))
		{
			foreach ($GLOBALS['TL_HOOKS']['getLanguages'] as $callback)
			{
				static::importStatic($callback[0])->{$callback[1]}($return, $languages, $langsNative, $blnInstalledOnly);
			}
		}

		return $return;
	}
Return the available languages as array

@param boolean $blnInstalledOnly If true, return only installed languages

@return array An array of languages