app\Certificate::getExpirationInterval PHP Method

    public function getExpirationInterval()
    {
        $pluralize = function ($count, $text) {
            return $count . ($count == 1 ? " {$text}" : " {$text}s");
        };
        $interval = (new \DateTime('now'))->diff($this->getExpirationDate());
        $string = '';
        if ($v = $interval->m >= 1) {
            $string .= $pluralize($interval->m, 'month') . ' ';
        }
        if ($v = $interval->d >= 1) {
            $string .= $pluralize($interval->d, 'day');
        }
        $string .= $interval->invert ? ' ago' : '';
        return $string;
    }