app\models\Invoice::getDueDate PHP Метод

    public function getDueDate($invoice_date = null)
    {
        if (!$this->is_recurring) {
            return $this->due_date ? $this->due_date : null;
        } else {
            $now = time();
            if ($invoice_date) {
                // If $invoice_date is specified, all calculations are based on that date
                if (is_numeric($invoice_date)) {
                    $now = $invoice_date;
                } else {
                    if (is_string($invoice_date)) {
                        $now = strtotime($invoice_date);
                    } elseif ($invoice_date instanceof \DateTime) {
                        $now = $invoice_date->getTimestamp();
                    }
                }
            }
            if ($this->due_date && $this->due_date != '0000-00-00') {
                // This is a recurring invoice; we're using a custom format here.
                // The year is always 1998; January is 1st, 2nd, last day of the month.
                // February is 1st Sunday after, 1st Monday after, ..., through 4th Saturday after.
                $dueDateVal = strtotime($this->due_date);
                $monthVal = (int) date('n', $dueDateVal);
                $dayVal = (int) date('j', $dueDateVal);
                $dueDate = false;
                if ($monthVal == 1) {
                    // January; day of month
                    $currentDay = (int) date('j', $now);
                    $lastDayOfMonth = (int) date('t', $now);
                    $dueYear = (int) date('Y', $now);
                    // This year
                    $dueMonth = (int) date('n', $now);
                    // This month
                    $dueDay = $dayVal;
                    // The day specified for the invoice
                    if ($dueDay > $lastDayOfMonth) {
                        // No later than the end of the month
                        $dueDay = $lastDayOfMonth;
                    }
                    if ($currentDay >= $dueDay) {
                        // Wait until next month
                        // We don't need to handle the December->January wraparaound, since PHP handles month 13 as January of next year
                        $dueMonth++;
                        // Reset the due day
                        $dueDay = $dayVal;
                        $lastDayOfMonth = (int) date('t', mktime(0, 0, 0, $dueMonth, 1, $dueYear));
                        // The number of days in next month
                        // Check against the last day again
                        if ($dueDay > $lastDayOfMonth) {
                            // No later than the end of the month
                            $dueDay = $lastDayOfMonth;
                        }
                    }
                    $dueDate = mktime(0, 0, 0, $dueMonth, $dueDay, $dueYear);
                } else {
                    if ($monthVal == 2) {
                        // February; day of week
                        $ordinals = ['first', 'second', 'third', 'fourth'];
                        $daysOfWeek = ['sunday', 'monday', 'tuesday', 'wednesday', 'thursday', 'friday', 'saturday'];
                        $ordinalIndex = ceil($dayVal / 7) - 1;
                        // 1-7 are "first"; 8-14 are "second", etc.
                        $dayOfWeekIndex = ($dayVal - 1) % 7;
                        // 1,8,15,22 are Sunday, 2,9,16,23 are Monday, etc.
                        $dayStr = $ordinals[$ordinalIndex] . ' ' . $daysOfWeek[$dayOfWeekIndex];
                        // "first sunday", "first monday", etc.
                        $dueDate = strtotime($dayStr, $now);
                    }
                }
                if ($dueDate) {
                    return date('Y-m-d', $dueDate);
                    // SQL format
                }
            } else {
                if ($this->client->payment_terms != 0) {
                    // No custom due date set for this invoice; use the client's payment terms
                    $days = $this->client->payment_terms;
                    if ($days == -1) {
                        $days = 0;
                    }
                    return date('Y-m-d', strtotime('+' . $days . ' day', $now));
                }
            }
        }
        // Couldn't calculate one
        return null;
    }