function _getRequiredLanguages() {
		$languages = get_option( 'pressbooks_global_typography', [] );
		$book_lang = $this->_getBookLanguage();

		if ( ! empty( $book_lang ) ) {
			$languages[] = $book_lang;
		}

		if ( is_array( $this->getThemeSupportedLanguages() ) ) {
			$languages = array_unique(
				array_merge( $languages, $this->getThemeSupportedLanguages() )
			);
		}

		return $languages;
	}
function _getRequiredLanguages() {
		$languages = get_option( 'pressbooks_global_typography', [] );
		$book_lang = $this->_getBookLanguage();

		if ( ! empty( $book_lang ) ) {
			$languages[] = $book_lang;
		}

		if ( is_array( $this->getThemeSupportedLanguages() ) ) {
			$languages = array_unique(
				array_merge( $languages, $this->getThemeSupportedLanguages() )
			);
		}

		return $languages;
	}
function _getRequiredLanguages ( ) { $ languages = get_option ( 'pressbooks_global_typography' , [ ] ) ; $ book_lang = $ this -> _getBookLanguage ( ) ; if ( ! empty ( $ book_lang ) ) { $ languages [ ] = $ book_lang ; } if ( is_array ( $ this -> getThemeSupportedLanguages ( ) ) ) { $ languages = array_unique ( array_merge ( $ languages , $ this -> getThemeSupportedLanguages ( ) ) ) ; } return $ languages ; }
Get required languages for this book, excluding those supported by the theme.

@return array
Get required languages for this book excluding those supported by the theme .