Monthly Commission Calculation PHP - php

Question

I'm running into a coder's block with PHP dates. Let me first paint the picture of what I want to happen. ex:
$user_join_date = new DateTime('2015-01-31');
$today_date = new DateTime('2015-04-30');
Every day a cron will be run and for this example, on every 31st (or 30th - 28th depending on the month) the system will calculate commission for this user based on orders and volume from the past month BETWEEN '2015-03-31' AND '2015-04-29'.
So what I need is two fold. First, I need to make sure I'm calculating the commission on the correct day ie: the monthly anniversary of their join date OR that same month's equivalent. Second, I need to find the time frame in between which I'll calculate commissions as demonstrated in the mysql snippit above.
For obvious reasons I can't just say:
if ($user_join_date->format('d') == $today_date->format('d')){
calc_commission();
}
Because this wouldn't get run every month. Let me know if I'm unclear on anything.

Answer 1

I think you're saying you want to credit each user on an integral number of months since her signup date. There's an aspect of MySQL's date arithmetic you will find very convenient -- INTERVAL n MONTH addition.
DATE('2015-01-30') + INTERVAL 1 MONTH ==> '2016-02-28'
DATE('2016-01-30') + INTERVAL 1 MONTH ==> '2016-02-29'
This feature deals with all the oddball Gregorian Calendar trouble around weekdays, quite nicely. I'm going to call the date the renewal date.
Now, let us say that the column signup contains the date/time stamp for when the user signed up. This expression determines the most recent monthly renewal date. In particular, if it is equal to CURDATE(), today is the renewal date.
DATE(signup) + INTERVAL TIMESTAMPDIFF(MONTH, DATE(signup), CURDATE()) MONTH
Next: This closely related (duh!) expression is equal to the previous month's renewal date.
DATE(signup) + INTERVAL TIMESTAMPDIFF(MONTH, DATE(signup), CURDATE())-1 MONTH
You could just take CURDATE() - INTERVAL 1 MONTH but this is much more accurate around Gregorian month-end monkey business. Try it: it works right even at the end of February 2016 (leap year day).
Now, you'll want to use transactions that happened beginning on the previous renewal date >=, up until the end of the day before < the present renewal date, in your computation. In MySQL filtering by that date range looks like this.
WHERE transdate >= DATE(signup) +
INTERVAL TIMESTAMPDIFF(MONTH, DATE(signup), CURDATE())-1 MONTH
AND transdate < DATE(signup) +
INTERVAL TIMESTAMPDIFF(MONTH, DATE(signup), CURDATE()) MONTH

Answer 2

$base_dt is your joining date. So If you pass it to checkIt function It will provide you true or false accordingly today's day is billing day or not.
$base_dt = new DateTime('2015-04-30', new DateTimeZone("America/Chicago"));
if(checkIt($base_dt)) {
echo "true";
//this is the day.
} else {
echo "false";
//this is not the day.
}
So the check it function should be like this .....
function checkIt($base_dt) {
$base_d = $base_dt->format('j'); //without zeroes
echo $base_d;
$today = new DateTime('now');
$d = $today->format('j');
echo $d;
if($base_d == $d) {
return true;
} else if($base_d>28) {
$base_dt->modify('last day of this month');
$dif_base = $base_dt->format('j') - $base_d;
//echo $dif_base;
$today->modify('last day of this month');
$diff_today = $today->format('j') - $d;
//echo $diff_today;
if(($base_d==31 && $diff_today==0)||($base_d==30 && $diff_today==0 && $d<30)||($base_d==29 && $diff_today==0 && $d<29)) {
return true;
}
if($dif_base==0 && $diff_today==0) {
return true;
}
}
return false;
}