How to combine date ranges in PHP

Hola
November 27, 2023
116 views
0 votes
2 Answers

I have an array that have start_date, end_date and price Eg.

/* date formate 'yyyy-mm-dd' */

$existingRanges = [
  ['start_date' => '2023-11-22', 'end_date' => '2023-11-30', 'price' => 200],
  ['start_date' => '2023-12-10', 'end_date' => '2023-12-14', 'price' => 100],
  ['start_date' => '2023-12-15', 'end_date' => '2023-12-20', 'price' => 100],
  ['start_date' => '2023-12-21', 'end_date' => '2023-12-27', 'price' => 100],
  ['start_date' => '2024-01-05', 'end_date' => '2024-01-05', 'price' => 600],
  ['start_date' => '2024-01-06', 'end_date' => '2024-01-07', 'price' => 700],
  ['start_date' => '2024-01-08', 'end_date' => '2024-01-20', 'price' => 700],
  ['start_date' => '2024-01-21', 'end_date' => '2024-01-31', 'price' => 100],
];

I want here to merge all the dates which are next to each other but have the same prices ie 2024-01-06 to 2024-01-07 and 2024-01-08 to 2024-01-20 these two date ranges are next to each other and their prices are the same so it should be 2024-01-06 to 2024-01-20 and price 700.

Array example of my results.

$results = [
  ['start_date' => '2023-11-22', 'end_date' => '2023-11-30', 'price' => 200],
  ['start_date' => '2023-12-10', 'end_date' => '2023-12-27', 'price' => 100],
  ['start_date' => '2024-01-05', 'end_date' => '2024-01-05', 'price' => 600],
  ['start_date' => '2024-01-06', 'end_date' => '2024-01-20', 'price' => 700],
  ['start_date' => '2024-01-21', 'end_date' => '2024-01-31', 'price' => 100],
];

The code/logic I tried with

function mergeDateRanges($p_arrDateranges) {
  // sort by start date
  /* usort($p_arrDateranges, function($a1, $a2) {
    return $a1['start_date'] === $a2['start_date'] ? 0 : ($a1['start_date'] < $a2['start_date'] ? -1 : 1);
   }); */

   $finalArray = [];
   $arrMerged = array();
   $arrLastDR = null;
   foreach ($p_arrDateranges as $arrDR) {

     if ($arrLastDR === null) {
       $arrLastDR = $arrDR;
       continue;
     }

     if(!$arrMerged) {
      array_push($arrMerged, $arrLastDR);
     }

     $endDate = DateTime::createFromFormat('Y-m-d', $arrLastDR['end_date']);
     $sLastDateE_1 = $endDate->modify('+1 day')->format('Y-m-d');

     if (strtotime($arrDR['start_date']) < strtotime($sLastDateE_1) && $arrDR['price'] == $arrLastDR['price']) {
       array_push($finalArray, [
         'start_date' => $arrDR['start_date'], 
         'end_date' => $arrLastDR['end_date'], 
         'price' => 0
       ]);
     } else {
       array_push($finalArray, $arrDR);
     }

     $arrLastDR = $arrDR;
     array_push($arrMerged, $arrLastDR);
     //print_r($arrLastDR);
 }

 return $finalArray;
}

mergeDateRanges($existingRanges);

This is returning different results So please help me to solve this issue.

Tags: algorithm php

Answers

If the time comparison of the previous end date equals current start date, along with the price check, then only update the end date of $arrLastDR to the current one’s end date(we can call this merging).

If they don’t match, this merge segment was only valid till this index. So, add that to $finalArray and start a new $arrLastDR with the current one.

So change the below

if(!$arrMerged) { array_push($arrMerged, $arrLastDR); } $endDate = DateTime::createFromFormat('Y-m-d', $arrLastDR['end_date']); $sLastDateE_1 = $endDate->modify('+1 day')->format('Y-m-d'); if (strtotime($arrDR['start_date']) < strtotime($sLastDateE_1) && $arrDR['price'] == $arrLastDR['price']) { array_push($finalArray, [ 'start_date' => $arrDR['start_date'], 'end_date' => $arrLastDR['end_date'], 'price' => 0 ]); } else { array_push($finalArray, $arrDR); } $arrLastDR = $arrDR; array_push($arrMerged, $arrLastDR);

 $endDate = DateTime::createFromFormat('Y-m-d', $arrLastDR['end_date']);
     $sLastDateE_1 = $endDate->modify('+1 day')->format('Y-m-d');

     if (strtotime($arrDR['start_date']) == strtotime($sLastDateE_1) && $arrDR['price'] == $arrLastDR['price']) {
        $arrLastDR['end_date'] = $arrDR['end_date'];
     }else{
        array_push($finalArray, $arrLastDR);
        $arrLastDR = $arrDR;
     }
     
    }
    
    if($arrLastDR !== null){
        array_push($finalArray, $arrLastDR);
    }

Live Demo

Note: No need of any explicit sorting since you already confirmed that the input is in a sorted manner.

Here is an alternate solution:

<?php

/*

Question Author: Hola
Question Answerer: Jacob Mulquin
Question: How to combine date ranges in PHP
URL: https://stackoverflow.com/questions/77555919/how-to-combine-date-ranges-in-php
Tags: php, algorithm

*/

$existingRanges = [
  ['start_date' => '2023-11-22', 'end_date' => '2023-11-30', 'price' => 200],
  ['start_date' => '2023-12-10', 'end_date' => '2023-12-14', 'price' => 100],
  ['start_date' => '2023-12-15', 'end_date' => '2023-12-20', 'price' => 100],
  ['start_date' => '2023-12-22', 'end_date' => '2023-12-27', 'price' => 100], // I modified this one to demonstrate non-contiguous date ranges with same price
  ['start_date' => '2024-01-05', 'end_date' => '2024-01-05', 'price' => 600],
  ['start_date' => '2024-01-06', 'end_date' => '2024-01-07', 'price' => 700],
  ['start_date' => '2024-01-08', 'end_date' => '2024-01-20', 'price' => 700],
  ['start_date' => '2024-01-21', 'end_date' => '2024-01-31', 'price' => 100],
];

function mergeDateRangesByPrice($ranges)
{
  $output = [];
  $tempRange = [];
  foreach ($ranges as $i => $range) {

    if (empty($tempRange)) {
      $tempRange = $range;
      continue;
    }

    // If a new price is found, lock in the tempRange and re-assign
    if ($range['price'] !== $tempRange['price']) {
      $output[] = $tempRange;
      $tempRange = $range;

      // If this is the last element but a new price, add to output array
      if ($i == count($ranges)-1) {
        $output[] = $range;
      }
      continue;
    }

    $rangeStartDate = strtotime($range['start_date']);
    $tempRangeEndDatePlusOneDay = strtotime("+1 day", strtotime($tempRange['end_date']));

    // Contiguous end date/start date, update the end_date of the tempRange
    if ($tempRangeEndDatePlusOneDay === $rangeStartDate) {
      $tempRange['end_date'] = $range['end_date'];
      continue;
    }
    
    // Non-contiguous end date/start date, lock in the tempRange and reassign    
    $output[] = $tempRange;
    $tempRange = $range;
  }
  return $output;
} 

$output = mergeDateRangesByPrice($existingRanges);

var_export($output);

Yields:

array (
  0 => 
  array (
    'start_date' => '2023-11-22',
    'end_date' => '2023-11-30',
    'price' => 200,
  ),
  1 => 
  array (
    'start_date' => '2023-12-10',
    'end_date' => '2023-12-20',
    'price' => 100,
  ),
  2 => 
  array (
    'start_date' => '2023-12-22',
    'end_date' => '2023-12-27',
    'price' => 100,
  ),
  3 => 
  array (
    'start_date' => '2024-01-05',
    'end_date' => '2024-01-05',
    'price' => 600,
  ),
  4 => 
  array (
    'start_date' => '2024-01-06',
    'end_date' => '2024-01-20',
    'price' => 700,
  ),
  5 => 
  array (
    'start_date' => '2024-01-21',
    'end_date' => '2024-01-31',
    'price' => 100,
  ),
)

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