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Calculate a proration percentage given the current timestamp and a current billing period
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| <?php | |
| /** | |
| * Handle calculating a percentage/fraction (proration) we should charge the | |
| * user for based on the current day of the month before their next bill cycle. | |
| * To use yourself, implement a getSubscription method which returns an object | |
| * containing current_period_start and current_period_end DateTime objects. | |
| * | |
| * @access public | |
| * @return float | |
| */ | |
| function prorateUpcomingBillingCycle() | |
| { | |
| $now = new DateTime('now', new DateTimeZone('UTC')); | |
| // determine the next billing cycle | |
| $subscription = getSubscription(); | |
| $currentPeriodStart = $subscription->current_period_start; | |
| $currentPeriodEnd = $subscription->current_period_end; | |
| if (is_string($currentPeriodStart)) { | |
| $currentPeriodStart = new DateTime($currentPeriodStart, new DateTimeZone('UTC')); | |
| } | |
| if (is_string($currentPeriodEnd)) { | |
| $currentPeriodEnd = new DateTime($currentPeriodEnd, new DateTimeZone('UTC')); | |
| } | |
| // get the number of second difference between the cycle start and end date | |
| $currentPeriodStartEpoch = (int) $currentPeriodStartEpoch->format('U'); | |
| $currentPeriodEndEpoch = (int) $currentPeriodEndEpoch->format('U'); | |
| $nowEpoch = (int) $now->format('U'); | |
| // if we aren't between the start and end of the subscription period, we have a problem | |
| if ($nowEpoch < $currentPeriodStartEpoch || $nowEpoch > $currentPeriodEndEpoch) { | |
| throw new Exception('The current timestamp does not fall within the current subscription period.'); | |
| } | |
| // get the difference of the start and end time in seconds | |
| $epochDifference = $currentPeriodEndEpoch - $currentPeriodStartEpoch; | |
| // get the prorated number of seconds till the end of the subscription period | |
| $remainingSecondsInPeriod = $currentPeriodEndEpoch - $nowEpoch; | |
| // return fraction of the total seconds in the current billing period | |
| return $remainingSecondsInPeriod / $epochDifference; | |
| } | |
| /** | |
| * Returns an example subscription object with a 30 day subscription period. | |
| * | |
| * This is only for reference. | |
| * | |
| * @return object | |
| */ | |
| function getSubScription() | |
| { | |
| $now = new DateTime('now', new DateTimeZone('UTC')); | |
| $obj = new stdClass(); | |
| $obj->current_period_start = clone $now; | |
| $obj->current_period_start->sub(new DateInterval('P15D'); | |
| $obj->current_period_end = clone $now; | |
| $obj->current_period_end->add(new DateInterval('P15D'))); | |
| return $obj; | |
| } |
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