PHP combine two seperate conflicting date ranges into unique pairs

Question

Set one:

1. 2014-04-05 To 2014-06-27
2. 2014-06-28 To 2014-10-19

Set two:

1. 2014-04-05 To 2014-05-02
2. 2014-05-03 To 2014-05-31
3. 2014-06-01 To 2014-10-19

What I need this to output is:

1. 2014-04-05 To 2014-05-02
2. 2014-05-03 To 2014-05-31
3. 2014-06-01 To 2014-06-27
4. 2014-06-28 To 2014-10-19

I attempted to use a function to check for overlaps as such:

!($lhs['RecordOnset'] > $rhs['RecordOffset'] || $lhs['RecordOffset'] < $rhs['RecordOnset'])

And used a for loop to check for the overlap:

for($i = 1; $i < sizeof($arr1); $i++) {
    for($j = 1; $j < sizeof($arr2); $j++) {
        $record = $arr1[$i];
        if($result = $this->intersects($arr1[$i], $arr2[$j])) {
            // $result;
        }
    }
}

The issue that I'm having is when I break a date range out, it doesn't check the new range that was created when looping. I do not have the ability to use SQL with this so I must come up with a programmatic solution. I've tried several different methods including some foreach loops.

The data is received in a date format as show in an array like such:

$arr1 = array(array('start'=>'04/05/2014', 'end'=> '2014-06-27'), array('start'=>'2014-06-28', 'end'=> '2014-10-19'));

$arr2 = array(array('start'=>'04/05/2014', 'end'=> '2014-05-02'), array('start'=>'2014-05-03', 'end'=> '2014-05-31'),array('start'=>'2014-06-01', 'end'=> '2014-10-19'));

The second pair would be a separate array, since it may have the same keys.

Any guidance or help with this is greatly appreciated. Date ranges with PHP has very limited resource online.

Answer 1

Usage : $output = mergeRanges($input);

This method is originally designed to merge any kind on numeric ranges, timestamps included and supports any kind of overlaps. It takes an array of objects in input, containing "from" and "to" keys which is customizable.

/**
 * @param        $ranges
 * @param string $keyFrom
 * @param string $keyTo
 *
 * @return array
 */
function mergeRanges($ranges, $keyFrom = 'from', $keyTo = 'to')
{
    // Split from / to values.
    $arrayFrom = [];
    $arrayTo   = [];
    foreach ($ranges as $date)
    {
        $arrayFrom[] = $date->$keyFrom;
        $arrayTo[]   = $date->$keyTo;
    }

    // Sort ASC.
    natsort($arrayFrom);
    natsort($arrayTo);

    $ranges = [];
    // Iterate over start dates.
    foreach ($arrayFrom as $indexFrom => $from)
    {
        // Get previous entry.
        $previousEntry = end($ranges);
        // Find associated default "to" value to "from" one.
        $to = $arrayTo[$indexFrom];

        // If we have a previous entry and "to" is greater than
        // current "from" value.
        if (isset($previousEntry->to) && $from < $previousEntry->to + 1)
        {
            // Do nothing if this range is completely covered
            // by the previous one.
            if ($to > $previousEntry->to)
            {
                // We just change te "to" value of previous range,
                // so we don't create a new entry.
                $previousEntry->to = $to;
            }
        }
        else
        {
            // Create a new range entry.
            $ranges[] = (object) [
                $keyFrom => $from,
                $keyTo   => $to,
            ];
        }
    }

    return $ranges;
}

Example :

$input = [
    // One day.
    (object) [
        'title' => 'One day.',
        'from'  => 1560816000,
        'to'    => 1560902399,
    ],
    // Same day, inner period
    (object) [
        'title' => 'Same day, inner period',
        'from'  => 1560816000 + 1000,
        'to'    => 1560902399 - 1000,
    ],
    // Just before midnight
    (object) [
        'title' => 'Just before midnight',
        'from'  => 1560816000 - 1000,
        'to'    => 1560816000 + 1000,
    ],
    // Just after midnight
    (object) [
        'title' => 'Just after midnight',
        'from'  => 1560902399 - 1000,
        'to'    => 1560902399 + 1000,
    ],
    // Other period before
    (object) [
        'title' => 'Other period before',
        'from'  => 1560902399 - 100000,
        'to'    => 1560902399 - 100000 + 5000,
    ],
    // Other period after
    (object) [
        'title' => 'Other period after',
        'from'  => 1560816000 + 100000,
        'to'    => 1560902399 + 100000 + 5000,
    ],
];

Result :

Array
(
    [0] => Array
        (
            [from] => 2019-06-17 22:13:19
            [to] => 2019-06-17 23:36:39
        )

    [1] => Array
        (
            [from] => 2019-06-18 01:43:20
            [to] => 2019-06-19 02:16:39
        )

    [2] => Array
        (
            [from] => 2019-06-19 05:46:40
            [to] => 2019-06-20 07:09:59
        )

)