public static function getInstance(Spreadsheet $spreadsheet = null)
    {
        if ($spreadsheet !== null) {
            $instance = $spreadsheet->getCalculationEngine();
            if (isset($instance)) {
                return $instance;
            }
        }

        if (!isset(self::$instance) || (self::$instance === null)) {
            self::$instance = new self();
        }

        return self::$instance;
    }
public static function getInstance(Spreadsheet $spreadsheet = null)
    {
        if ($spreadsheet !== null) {
            $instance = $spreadsheet->getCalculationEngine();
            if (isset($instance)) {
                return $instance;
            }
        }

        if (!isset(self::$instance) || (self::$instance === null)) {
            self::$instance = new self();
        }

        return self::$instance;
    }
public static function getInstance ( Spreadsheet $ spreadsheet = null ) { if ( $ spreadsheet !== null ) { $ instance = $ spreadsheet -> getCalculationEngine ( ) ; if ( isset ( $ instance ) ) { return $ instance ; } } if ( ! isset ( self :: $ instance ) || ( self :: $ instance === null ) ) { self :: $ instance = new self ( ) ; } return self :: $ instance ; }
Get an instance of this class.

@param Spreadsheet $spreadsheet Injected spreadsheet for working with a PhpSpreadsheet Spreadsheet object,
or NULL to create a standalone claculation engine

@return Calculation
Get an instance of this class .