Find NOW() within two odd date selections - php

Question

I have used numorous date functions in the past, but I need help on a specific function...
Is there a function where I can assign two unknown dates and the system knows where I am within these two dates? Let me explain:
Our monthly salaries run from the 23rd of each month to the 22nd of the next month. Because earnings work on an hourly basis, my boss wants to know anywhere within the month where the accumulative salaries are. For instance the salary period started on the 23rd of September 2012 and we are now on the 29th, I want my query to be able to know where we are in the current salary period.
As you know, months move on, thus my script must automatically know in which period and where whithin that period we are now.
I can do the queries surrounding this, I just need to know the date function (s) to use to assign this array...
Any help will be appreciated - Thanx

Answer 1

You can use PHP's DateTime classes to do this quite easily:-
$periodStart = new DateTime('23rd September');
$now = new DateTime();
$interval = $now->diff($periodStart);
echo "We are {$interval->d} days into the payment period";
Output:
We are 6 days into the payment period.
I prefer to extend the DateTime class for this kind of thing, so everything is in the same place:-
class MyDateTime extends DateTime
{
public function elapsedDays(DateTime $since = null)
{
if ($since === null) {
$since = new DateTime();
}
$interval = $since->diff($this);
return (int) $interval->d;
}
}
$periodStart = new MyDateTime('23rd September');
echo "We are {$periodStart->elapsedDays()} days into the payment period";
Gives the same output.
You can then create periods and intervals and iterate over it to aggregate the sum like:
$datePeriodStart = new DateTime('23rd September');
$datePeriodEnd = clone $datePeriodStart;
$datePeriodEnd->add(new DateInterval('P1M'));
$dateToday = new DateTime();
$interval1 = $dateToday->diff($datePeriodStart);
$interval2 = $dateToday->diff($datePeriodEnd);
echo "We are {$interval1->d} day(s) into the payment period, {$interval2->d} day(s) left.\n";
$period = new DatePeriod($datePeriodStart, new DateInterval('P1D'), $dateToday);
$days = new IteratorIterator($period);
$totalSalary = 0;
$totalDays = 0;
foreach($days as $day)
{
$salary = get_salary_for_day($day);
$totalSalary += $salary;
$totalDays++;
printf("#%d: %s %s\n", $totalDays, $day->format('Y-m-d'), number_format($salary));
}
printf("Total Salary for %d day(s): %s\n", $totalDays, number_format($totalSalary));
Example output:
We are 6 day(s) into the payment period, 23 day(s) left.
#1: 2012-09-23 12,500
#2: 2012-09-24 12,500
#3: 2012-09-25 12,500
#4: 2012-09-26 12,500
#5: 2012-09-27 12,500
#6: 2012-09-28 12,500
#7: 2012-09-29 12,500
Total Salary for 7 day(s): 87,500

Answer 2

You could simply use a TIMESTAMP value (seconds since epoch, also called a "unix timestamp") and just test to see if the current date in unix timestamp is in between the first and last unix timestamp dates.
Essentially, that way you are merely converting the date into a big integer (number of seconds since 1969/70), and arithmetic and testing functions become a LOT easier to handle.

Answer 3

Get FROM and TO date:
$to = new DateTime();
$from = new DateTime($to->format('Y-m-23'));
if ($to->format('j') < 23) {
$from->modify('-1 month');
}
Var_dump:
var_dump($from->format('Y-m-d')); # 2012-09-23
var_dump($to->format('Y-m-d')); # 2012-09-29
SQL
$sql = "
SELECT ...
FROM ...
WHERE some_time BETWEEN '" . $from->format('Y-m-d') . "' AND '" . $to->format('Y-m-d') ."'
";