At first I suggested using the DateTime class that PHP provides, naively assuming that it has some kind of thought-out API that one could use. It turns out that it does not. While it features very basic DateTime functionality, it is mostly unusable because, for most operations, it relies on the DateInterval class. In combination, those classes represent another masterpiece of bad API design.
An interval should be defined like so:
An interval in Joda-Time represents an interval of time from one millisecond instant to another instant. Both instants are fully specified instants in the datetime continuum, complete with time zone.
In PHP, however, an Interval is just a duration:
A date interval stores either a fixed amount of time (in years, months, days, hours etc) or a relative time string [such as "2 days"].
Unfortunately, PHP's DateInterval definition does not allow for intersection/overlap calculation (which the OP needs) because PHP's Intervals have no specific position in the datetime continuum. Therefore, I've implemented a (very rudimentary) class that adheres to JodaTime's definition of an interval. It is not extensively tested, but it should get the work done:
class ProperDateInterval {
private $start = null;
private $end = null;
public function __construct(DateTime $start, DateTime $end) {
$this->start = $start;
$this->end = $end;
}
/**
* Does this time interval overlap the specified time interval.
*/
public function overlaps(ProperDateInterval $other) {
$start = $this->getStart()->getTimestamp();
$end = $this->getEnd()->getTimestamp();
$oStart = $other->getStart()->getTimestamp();
$oEnd = $other->getEnd()->getTimestamp();
return $start < $oEnd && $oStart < $end;
}
/**
* Gets the overlap between this interval and another interval.
*/
public function overlap(ProperDateInterval $other) {
if(!$this->overlaps($other)) {
// I haven't decided what should happen here yet.
// Returning "null" doesn't seem like a good solution.
// Maybe ProperDateInterval::EMPTY?
throw new Exception("No intersection.");
}
$start = $this->getStart()->getTimestamp();
$end = $this->getEnd()->getTimestamp();
$oStart = $other->getStart()->getTimestamp();
$oEnd = $other->getEnd()->getTimestamp();
$overlapStart = NULL;
$overlapEnd = NULL;
if($start === $oStart || $start > $oStart) {
$overlapStart = $this->getStart();
} else {
$overlapStart = $other->getStart();
}
if($end === $oEnd || $end < $oEnd) {
$overlapEnd = $this->getEnd();
} else {
$overlapEnd = $other->getEnd();
}
return new ProperDateInterval($overlapStart, $overlapEnd);
}
/**
* @return long The duration of this interval in seconds.
*/
public function getDuration() {
return $this->getEnd()->getTimestamp() - $this->getStart()->getTimestamp();
}
public function getStart() {
return $this->start;
}
public function getEnd() {
return $this->end;
}
}
It may be used like so:
$seasonStart = DateTime::createFromFormat('j-M-Y', '01-Apr-2012');
$seasonEnd = DateTime::createFromFormat('j-M-Y', '30-Sep-2012');
$userStart = DateTime::createFromFormat('j-M-Y', '01-Jan-2012');
$userEnd = DateTime::createFromFormat('j-M-Y', '02-Apr-2012');
$i1 = new ProperDateInterval($seasonStart, $seasonEnd);
$i2 = new ProperDateInterval($userStart, $userEnd);
$overlap = $i1->overlap($i2);
var_dump($overlap->getDuration());
