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

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.

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