sort array based on the dateTime in php

Question

Array
        (
            [0] => Array
                (
                    [dateTime] => 2011-10-18 0:0:00
                    [chanl1] => 20.7
                    [chanl2] => 45.4
                    [chanl3] => 
                )

            [1] => Array
                (
                    [dateTime] => 2011-10-18 0:15:00
                    [chanl1] => 20.7
                    [chanl2] => 45.4
                    [chanl3] => 
                )


            [2] => Array
                (
                    [dateTime] => 2011-10-18 00:14:00
                    [chanl1] => 20.7
                    [chanl2] => 33.8
                    [chanl3] => 
                )

            [3] => Array
                (
                    [dateTime] => 2011-10-18 00:29:00
                    [chanl1] => 20.6
                    [chanl2] => 33.9
                    [chanl3] => 
                )

I want to sort the above array based on the [dateTime], the final output should be:

Array
        (
            [0] => Array
                (
                    [dateTime] => 2011-10-18 0:0:00
                    [chanl1] => 20.7
                    [chanl2] => 45.4
                    [chanl3] => 
                )

            [1] => Array
                (
                    [dateTime] => 2011-10-18 00:14:00
                    [chanl1] => 20.7
                    [chanl2] => 33.8
                    [chanl3] => 
                )

            [2] => Array
                (
                    [dateTime] => 2011-10-18 0:15:00
                    [chanl1] => 20.7
                    [chanl2] => 45.4
                    [chanl3] => 
                )            

            [3] => Array
                (
                    [dateTime] => 2011-10-18 00:29:00
                    [chanl1] => 20.6
                    [chanl2] => 33.9
                    [chanl3] => 
                )

Is there anyone know how to do it? Thanks!

The datetime data in this question is "Big-endian", so there is no need to parse the column values -- just [comparing them as strings is 100% reliable](https://stackoverflow.com/a/67124505/2943403). — mickmackusa, Aug 15 '22 at 20:02

score 64 · Answer 1 · edited Nov 29 '17 at 10:17

64

Use usort() function with custom comparator:

$arr = array(...);

usort($arr, function($a, $b) {
  $ad = new DateTime($a['dateTime']);
  $bd = new DateTime($b['dateTime']);

  if ($ad == $bd) {
    return 0;
  }

  return $ad < $bd ? -1 : 1;
});

DateTime class has overloaded comparison operators (<, >, ==).

edited Nov 29 '17 at 10:17

Andy

4,901
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answered Nov 14 '11 at 12:02

Crozin

43,890
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135

it should be usort(**$arr, **function($a, $b) but the rest is ok – Martin Holzhauer Nov 14 '11 at 12:05
3

@Crozin It is a common misconception that usort has to return `-1,0,1`. Like the manual states: *The comparison function must return an integer less than, equal to, or greater than zero if the first argument is considered to be respectively less than, equal to, or greater than the second.* and that means any value `<=>0`. – Gordon Nov 14 '11 at 12:34
3

@Gordon: Yeah, I know that fact, however if we're operating on something that is not a number (DateTime in this case) it's a common practice to return `±1`. – Crozin Nov 14 '11 at 13:04
2

Isn't the ternary backwards? Unless there's something silly that I'm missing, if the first value is less than the second then you should be returning a value <0. I think it should be ```return $ad < $bd ? -1 : 1;``` – John Pancoast Aug 07 '15 at 18:55
@JohnPancoast Or just return $ad > $bd ? 1 : -1 – Jaaaaaaay Mar 09 '16 at 04:29
@Jaaaaaaay Yea, yours has the same effect as mine but the OPs original was different. – John Pancoast Mar 10 '16 at 06:14
2

Note: switch -1 and 1 around to change general order to descending – Arnas Ziedavicius Dec 15 '16 at 10:58
3

I'm glad we can use the spaceship operator `<=>` in PHP 7. :) – Arvid Jan 07 '19 at 14:15

score 21 · Answer 2 · edited May 23 '17 at 10:31

21

For performance, this method using array_multisort is very efficient:

$ord = array();
foreach ($array as $key => $value){
    $ord[] = strtotime($value['dateTime']);
}
array_multisort($ord, SORT_ASC, $array);
print_r($array);

edited May 23 '17 at 10:31

Community

1
1

answered Aug 10 '13 at 11:43

Expedito

7,771
5
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43

1

I was trying to sort an array of datetime objects and this worked great for me. Thanks! I modified it a bit to just be ````array_multisort($array, SORT_ASC, $array);```` – thenomadicmann Oct 28 '20 at 21:18

score 14 · Answer 3 · answered Jan 09 '19 at 14:37

14

Simple sorting for DateTime objects with the spaceship operator:

$list = [
    new DateTime('yesterday'),
    new DateTime('today'),
    new DateTime('1 week ago'),
];

uasort($list, function ($a, $b) {
    return $a <=> $b;
});

var_dump($list);

answered Jan 09 '19 at 14:37

Stefan Pöltl

141
1
2

score 12 · Answer 4 · answered Nov 14 '11 at 12:01

12

Using uasort() with a custom sort callback should do it:

function cmp($a, $b) {
  if ($a['dateTime'] == $b['dateTime']) {
    return 0;
  }

  return ($a['dateTime'] < $b['dateTime']) ? -1 : 1;
}

uasort($arr, 'cmp');

uasort() preserves your array's keys, you can use usort() instead if you don't need that to happen.

answered Nov 14 '11 at 12:01

Clive

36,918
8
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113

1

You shouldn't compare string values with `<` operator. – Crozin Nov 14 '11 at 12:03
1

@Petah Because you are assuming a specific date format, Crozins answer is much more usable. – Digital Fu Sep 15 '14 at 02:48
2

@h.coates yes, you are correct that I am assuming it is in the format that is given in the sample data. Why would it not be? – Petah Sep 15 '14 at 20:38

score 5 · Answer 5 · edited Jul 02 '18 at 12:06

5

For php array and object this example is helpful for sorting...

For datetime descending:

usort($response_data['callback'], function($a, $b) {
   return strcasecmp(strtotime($b->view_date), strtotime($a->view_date));
});

For datetime ascending:

usort($response_data['callback'], function($a, $b) {
   return strtotime($a->view_date) - strtotime($b->view_date);
});

edited Jul 02 '18 at 12:06

Nico Haase

11,420
35
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answered Apr 02 '18 at 06:19

AngularJMK

1,178
13
15

I like the subtraction part of your solution. This is pretty neat and (at least for me) better to read than the whole `$a < $b ? -1 : ($a > $b ? 1 : 0)` stuff. … With a current PHP version I'd rather use the spaceship operator `<=>` but in single cases you can't just switch a running project to latest PHP version (as in my current case where the customer has some … "issues" with updating. ;)). – Arvid Jan 07 '19 at 14:14

score 3 · Answer 6 · 2011-11-14T12:35:27.060

Use array_multisort :

 <?php
        $myarray=array(
                    0 => array
                        (
                            'dateTime' => '2011-10-18 00:0:00',
                            'chanl1' => '20.7',
                            'chanl2' => '45.4',
                            'chanl3' => '',
                        ),

                    1 => array
                        (
                            'dateTime' => '2011-10-18 00:15:00',
                            'chanl1' => '20.7',
                            'chanl2' => '45.4',
                            'chanl3' => '',
                        ),
                  2 => array
                        (
                            'dateTime' => '2011-10-18 00:14:00',
                            'chanl1' => '20.7',
                            'chanl2' => '33.8',
                            'chanl3' => '',
                        ),

                    3 => array
                        (
                            'dateTime' => '2011-10-18 00:29:00',
                            'chanl1' => '20.6',
                            'chanl2' => '33.9',
                            'chanl3' => ''
                        ));

            foreach($myarray as $c=>$key) {
                    $dateTime[] = $key['dateTime'];
                $chanl1[] = $key['chanl1'];
                    $chanl2[] = $key['chanl2'];
                    $chanl3[] = $key['chanl3'];
            }

        array_multisort($dateTime,SORT_ASC,SORT_STRING,$myarray);   
        print_r($myarray);

sort array based on the dateTime in php

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