PHP DateInterval Jan - June and July - Dec - php

Question

Trying to create a list or date interval for the past 2 years, divided into ranges of 6 months, i.e. Jan - June 2015, July - Dec 2015, Jan - June 2016 ... until today.
I have looked into DateTime and DateInterval, something like this
$begin = new DateTime( '2015-01-01' );
$end = new DateTime( '2017-12-26' );
$interval = new DateInterval('P6M');
$period = new DatePeriod($begin, $interval, $end);
foreach ( $period as $dt )
echo sprintf("%s\n", $dt->format("Y-m-d"));
Which gives me
2015-01-01
2015-07-01
2016-01-01
2016-07-01
2017-01-01
2017-07-01
Can't figure out how to get start and end (Jan 1 - June 30 and July 1 - Dec 31) for each period.

Answer 1

After adding an interval, subtract one day from it. Use sub() and new DateInterval('P1D'), which indicates subtraction of one day.
foreach ( $period as $dt )
echo sprintf(
"%s %s\n",
$dt->format("Y-m-d"),
$dt->add($interval)
->sub(new DateInterval('P1D'))
->format("Y-m-d"));
This outputs:
2015-01-01 2015-06-30
2015-07-01 2015-12-31
2016-01-01 2016-06-30
2016-07-01 2016-12-31
2017-01-01 2017-06-30
2017-07-01 2017-12-31
Update: In the comments you also asked how to indicate what half of the year the date represents. The answer is too obvious:
sprintf(
"%s %s %d\n",
$dt->format("Y-m-d"),
$dt->add($interval)
->sub(new DateInterval('P1D'))
->format("Y-m-d"),
$dt->format("n")/6
);
Note %d and corresponding $dt->format("n")/6.
Output for me:
2015-01-01 2015-06-30 1
2015-07-01 2015-12-31 2
2016-01-01 2016-06-30 1
2016-07-01 2016-12-31 2
2017-01-01 2017-06-30 1
2017-07-01 2017-12-31 2

Answer 2

you can just add the interval size '-1' for each start like this:
$begin = new DateTime( '2015-01-01' );
$end = new DateTime( '2017-12-26' );
$interval = new DateInterval('P6M');
$period = new DatePeriod($begin, $interval, $end);
$oneDay = new DateInterval("P1D");
$oneDay->invert=1; #just get the previous day as if("P-1D")
foreach ( $period as $dt ){
echo $dt->format("Y-m-d"); #interval start
$dt->add($interval); #adding the interval size
$dt->add($oneDay); #get the last day of the cur interval
echo "<br>";
echo $dt->format("Y-m-d"); #interval end
echo "<br>";
}