public function getKeys(
        array $domains = [],
        array $languages = []
    ) : array {
        return array_reduce(
            $this->getTranslations(
                $domains,
                $languages
            ),
            function (array $keys, Translation $translation) {
                $keys[] = $translation->getKey();

                return $keys;
            },
            []
        );
    }
public function getKeys(
        array $domains = [],
        array $languages = []
    ) : array {
        return array_reduce(
            $this->getTranslations(
                $domains,
                $languages
            ),
            function (array $keys, Translation $translation) {
                $keys[] = $translation->getKey();

                return $keys;
            },
            []
        );
    }
public function getKeys ( array $ domains = [ ] , array $ languages = [ ] ) : array { return array_reduce ( $ this -> getTranslations ( $ domains , $ languages ) , function ( array $ keys , Translation $ translation ) { $ keys [ ] = $ translation -> getKey ( ) ; return $ keys ; } , [ ] ) ; }
Get available keys.

@param array $domains
@param array $languages

@return array
Get available keys .