php merge dateranges code algorithm

Here is a code for merging date-ranges in array. The method gives new array, with the maximum mergining between the date-ranges, meaning if there is a date-range that already exists with-in other, it can just skip, so just if two or more dates can be combined into one big date-range - it will be made :) . 

 

-------------------------------Example #1:

  array 
  0 => 's' => '2020-01-06' 'e' => '2020-01-10'
  1 => 's' => '2020-01-07' 'e' => '2020-01-12'
  2 => 's' => '2020-01-13' 'e' => '2020-01-16'
  3 => 's' => '2020-01-22' 'e' => '2020-01-24'

RESULT:
array 
  0 => 's' => '2020-01-06' 'e' => '2020-01-16'
  1 => 's' => '2020-01-22' 'e' => '2020-01-24'

 

-------------------------------Example #2:

array (size=8)
  0 => 's' => '2020-01-01' 'e' => '2020-01-01'
  1 => 's' => '2020-01-03' 'e' => '2020-01-03'
  2 => 's' => '2020-01-09' 'e' => '2020-01-10'
  3 => 's' => '2020-01-11' 'e' => '2020-01-22'
  4 => 's' => '2020-01-14' 'e' => '2020-02-02'
  5 => 's' => '2020-02-02' 'e' => '2020-02-03'
  6 => 's' => '2020-02-04' 'e' => '2020-02-04'
  7 => 's' => '2020-02-05' 'e' => '2020-02-07'

RESULT:
array (size=3)           
  0 => 's' => '2020-01-01' 'e' => '2020-01-01'
  1 => 's' => '2020-01-03' 'e' => '2020-01-03'
  2 => 's' => '2020-01-09' 'e' => '2020-02-07'

 

 

And here is the CODE:

$arrDateranges = array(
    array('s' => '2020-01-22', 'e' => '2020-01-24'),
    array('s' => '2020-01-06', 'e' => '2020-01-10'),
    array('s' => '2020-01-07', 'e' => '2020-01-12'),
    array('s' => '2020-01-13', 'e' => '2020-01-16'),
);
$arrMerged = mergeDateRanges($arrDateranges);
var_dump($arrDateranges);
var_dump($arrMerged);

//---------------------------------------------------------

// helper funciton to get NEXT date (or any modified date)
function getRelativeDate($p_sDate, $p_sModify, $p_sFormatIn = 'Y-m-d', $p_sFormatOut = 'Y-m-d') {
    $oDT = DateTime::createFromFormat($p_sFormatIn, $p_sDate);
    $oDT->modify($p_sModify);
    return $oDT->format($p_sFormatOut);
}

function mergeDateRanges($p_arrDateranges) {
    // sort by start date
    usort($p_arrDateranges, function($a1, $a2) {
        return $a1['s'] === $a2['s'] ? 0 : ($a1['s'] < $a2['s'] ? -1 : 1);
    });
    
    $arrMerged = array();
    $arrLastDR = null;
    foreach ($p_arrDateranges as $arrDR) {
        if ($arrLastDR === null) {
            $arrLastDR = $arrDR;
            continue;
        }
        //
        // NOTE: dateS is sorted thus $sDateS >= $arrLastDR['s']
        //
        if ($arrDR['e'] <= $arrLastDR['e']) {
            continue; // already in the range.
        }
        // --- [e] > lastDR[e] ---
        $sLastDateE_1 = getRelativeDate($arrLastDR['e'], '+1 day');
        if ($arrDR['s'] <= $sLastDateE_1) { // lapping date-range until day+1
            $arrLastDR['e'] = $arrDR['e'];
            continue;
        }

        // there is gap, so need to create new date-range
        array_push($arrMerged, $arrLastDR);
        $arrLastDR = $arrDR;
    }

    if ($arrLastDR === null) {
        array_push($arrMerged, $arrLastDR);
    }
    return $arrMerged;
}