How to get closest date compared to an array of dates in PHP

Question

This post almost answered this question for me, but I have a specific need and didn\'t find what I sought there. This lies right outside my experience; couldn\'t quite wrap

Answer 1

I may not have the best naming conventions, but here goes.

I calculate the intervals between the array of dates and the given date. I then do a sort, to find the "smallest" difference.

$dates = array
(
    '0'=> "2013-02-18 05:14:54",
    '1'=> "2013-02-12 01:44:03",
    '2'=> "2013-02-05 16:25:07",
    '3'=> "2013-01-29 02:00:15",
    '4'=> "2013-01-27 18:33:45"
);


function find_closest($array, $date)
{
    //$count = 0;
    foreach($array as $day)
    {
        //$interval[$count] = abs(strtotime($date) - strtotime($day));
        $interval[] = abs(strtotime($date) - strtotime($day));
        //$count++;
    }

    asort($interval);
    $closest = key($interval);

    echo $array[$closest];
}

find_closest($dates, "2013-02-18 05:14:55");

Answer 2

If I understand your question perfectly then this will solve your problem.

Tested Code

<?php
    $dates = array
    (
        '0' => "2013-02-18 05:14:54",
        '1' => "2013-02-12 01:44:03",
        '2' => "2013-02-05 16:25:07",
        '3' => "2013-01-29 02:00:15",
        '4' => "2013-01-27 18:33:45"
    );

    function closest($dates, $findate)
    {
        $newDates = array();

        foreach($dates as $date)
        {
            $newDates[] = strtotime($date);
        }

        echo "<pre>";
        print_r($newDates);
        echo "</pre>";

        sort($newDates);
        foreach ($newDates as $a)
        {
            if ($a >= strtotime($findate))
                return $a;
        }
        return end($newDates);
    }

    $values = closest($dates, date('2013-02-04 14:11:16'));
    echo date('Y-m-d h:i:s', $values);
?>

Answer 3

Just try this:

$date = array(
    [0]=> "2013-02-18 05:14:54"
    [1]=> "2013-02-12 01:44:03"
    [2]=> "2013-02-05 16:25:07"
    [3]=> "2013-01-29 02:00:15"
    [4]=> "2013-01-27 18:33:45");

$baseDate = date_create('2009-10-11');
$count = count($date);
for($loop=0;$count>$loop;$loop++) {
    $datetime = date_create($date[$loop]);
    $interval = date_diff($baseDate, $datetime);
    $newDate[$interval->format('%s')] = $date[$loop];
}
ksort($newDate);
foreach($newDate as $key=>$value) {
    echo $value;
    break;
}

Your first element will the the closest match date.

Note: Please test it before you use.

Answer 4

Suppose your array is bigger and that you have dates over the period 2009-10-01 to 2019-10-01. Lets now compare two approach: a. looping-array approach vs b. sorting-indexing-array approach.

<?php 

$period = new DatePeriod(
    new DateTime('2009-10-01 00:00:00'),
    new DateInterval('P3D'),
    new DateTime('2019-10-01 00:00:00')
);

foreach($period as $date){ 
    $dates[] = $date->format('Y-m-d'); 
};


$today = '2019-08-18 13:00:15';

function custom_sort($array){
  sort($array);
  return $array;
}

function nearest_date_key($array, $today){
    //push today to the array, sort the array, 
    //find the nearest day value of the sorted array and return key
    array_push($array, $today);
    $sorted_dates = custom_sort($array);
    $find_today_key = array_search($today, $sorted_dates);
    $nearest_date = array_slice($sorted_dates, $find_today_key + 1, 1);
    return array_search($nearest_date[0], $array);
}


function find_closest($array, $today)
{
    //$count = 0;
    foreach($array as $day)
    {
        //$interval[$count] = abs(strtotime($date) - strtotime($day));
        $interval[] = abs(strtotime($today) - strtotime($day));
        //$count++;
    }

    asort($interval);
    $closest = key($interval);
    return $closest;
}

$start = microtime(true);
$result_a = nearest_date_key($dates, $today);
$time_elapsed_secs_a = microtime(true) - $start;

$start = microtime(true);
$result_b = find_closest($dates, $today);
$time_elapsed_secs_b = microtime(true) - $start;
?>

Printing the results gives (http://phptester.net/)

                            result  time_elapsed
loop approach (a)           1203    0.00630   
sorting index approach (b)  1203    0.00062

Which is a huge time elapsed gain. We divided by ten the waiting time