Suppose the following huge array (I deliberately didn't remove any of its records so that you have a good amount of data in case someone wants to dig in and help me find a solution to my problem):
$program = array (
'2021-07-11' =>
array (
0 =>
array (
'movie' => 'Movie 1',
'channel' => 'Channel 10',
'time' => '23:00',
),
1 =>
array (
'movie' => 'Movie 2',
'channel' => 'Channel 2',
'time' => '01:15',
),
2 =>
array (
'movie' => 'Movie 8',
'channel' => 'Channel 4',
'time' => '11:00',
),
3 =>
array (
'movie' => 'Movie 12',
'channel' => 'Channel 11',
'time' => '17:30',
),
4 =>
array (
'movie' => 'Movie 14',
'channel' => 'Channel 5',
'time' => '21:00',
),
5 =>
array (
'movie' => 'Movie 15',
'channel' => 'Channel 5',
'time' => '02:20',
),
6 =>
array (
'movie' => 'Movie 17',
'channel' => 'Channel 11',
'time' => '17:30',
),
7 =>
array (
'movie' => 'Movie 19',
'channel' => 'Channel 5',
'time' => '10:00',
),
8 =>
array (
'movie' => 'Movie 21',
'channel' => 'Channel 8',
'time' => '1:20',
),
9 =>
array (
'movie' => 'Movie 33',
'channel' => 'Channel 5',
'time' => '00:20',
),
10 =>
array (
'movie' => 'Movie 39',
'channel' => 'Channel 3',
'time' => '17:30',
),
11 =>
array (
'movie' => 'Movie 40',
'channel' => 'Channel 3',
'time' => '22:00',
),
12 =>
array (
'movie' => 'Movie 41',
'channel' => 'Channel 5',
'time' => '14:00',
),
13 =>
array (
'movie' => 'Movie 42',
'channel' => 'Channel 5',
'time' => '23:00',
),
14 =>
array (
'movie' => 'Movie 43',
'channel' => 'Channel 2',
'time' => '14:15',
),
15 =>
array (
'movie' => 'Movie 44',
'channel' => 'Channel 2',
'time' => '18:00',
),
16 =>
array (
'movie' => 'Movie 45',
'channel' => 'Channel 2',
'time' => '23:45',
),
17 =>
array (
'movie' => 'Movie 46',
'channel' => 'Channel 1',
'time' => '22:00',
),
18 =>
array (
'movie' => 'Movie 47',
'channel' => 'Channel 6',
'time' => '21:10',
),
),
'2021-07-10' =>
array (
0 =>
array (
'movie' => 'Movie 3',
'channel' => 'Channel 2',
'time' => '14:15',
),
1 =>
array (
'movie' => 'Movie 5',
'channel' => 'Channel 3',
'time' => '22:00',
),
2 =>
array (
'movie' => 'Movie 6',
'channel' => 'Channel 11',
'time' => '23:00',
),
3 =>
array (
'movie' => 'Movie 7',
'channel' => 'Channel 4',
'time' => '11:15',
),
4 =>
array (
'movie' => 'Movie 11',
'channel' => 'Channel 4',
'time' => '21:00',
),
5 =>
array (
'movie' => 'Movie 16',
'channel' => 'Channel 2',
'time' => '23:45',
),
6 =>
array (
'movie' => 'Movie 20',
'channel' => 'Channel 4',
'time' => '23:00',
),
7 =>
array (
'movie' => 'Movie 23',
'channel' => 'Channel 5',
'time' => '01:00',
),
8 =>
array (
'movie' => 'Movie 27',
'channel' => 'Channel 4',
'time' => '01:00',
),
9 =>
array (
'movie' => 'Movie 29',
'channel' => 'Channel 7',
'time' => '02:15',
),
10 =>
array (
'movie' => 'Movie 31',
'channel' => 'Channel 5',
'time' => '14:00',
),
11 =>
array (
'movie' => 'Movie 32',
'channel' => 'Channel 5',
'time' => '22:10',
),
12 =>
array (
'movie' => 'Movie 36',
'channel' => 'Channel 2',
'time' => '00:01',
),
13 =>
array (
'movie' => 'Movie 37',
'channel' => 'Channel 2',
'time' => '11:30',
),
14 =>
array (
'movie' => 'Movie 38',
'channel' => 'Channel 6',
'time' => '22:30',
),
),
'2021-07-09' =>
array (
0 =>
array (
'movie' => 'Movie 4',
'channel' => 'Channel 5',
'time' => '21:00',
),
1 =>
array (
'movie' => 'Movie 9',
'channel' => 'Channel 11',
'time' => '22:00',
),
2 =>
array (
'movie' => 'Movie 10',
'channel' => 'Channel 9',
'time' => '16:45',
),
3 =>
array (
'movie' => 'Movie 18',
'channel' => 'Channel 7',
'time' => '22:00',
),
4 =>
array (
'movie' => 'Movie 22',
'channel' => 'Channel 5',
'time' => '23:00',
),
5 =>
array (
'movie' => 'Movie 24',
'channel' => 'Channel 9',
'time' => '21:00',
),
6 =>
array (
'movie' => 'Movie 25',
'channel' => 'Channel 9',
'time' => '23:00',
),
7 =>
array (
'movie' => 'Movie 26',
'channel' => 'Channel 4',
'time' => '21:00',
),
8 =>
array (
'movie' => 'Movie 28',
'channel' => 'Channel 8',
'time' => '23:00',
),
9 =>
array (
'movie' => 'Movie 30',
'channel' => 'Channel 6',
'time' => '23:45',
),
10 =>
array (
'movie' => 'Movie 34',
'channel' => 'Channel 3',
'time' => '23:00',
),
11 =>
array (
'movie' => 'Movie 35',
'channel' => 'Channel 2',
'time' => '22:00',
),
),
'2021-07-12' =>
array (
0 =>
array (
'movie' => 'Movie 13',
'channel' => 'Channel 5',
'time' => '01:20',
),
),
)
I want to sort this array by date (the keys of the first dimension), and by the column time of the third dimension, so that I end up with a list of movies grouped by date, and sorted by their broadcast time...
The first task is a super easy one-liner...
array_multisort(array_map('strtotime', array_keys($program)), SORT_ASC, $program);
The second task however is giving me a hard time to implement in a similar elegant way... What I tried was this:
array_multisort(array_map('strtotime', array_keys($program)), SORT_ASC, array_column($program, 'time'), SORT_ASC, $program);
but this doesn't work as for some reason array_column($program, 'time') returns an empty array. In the manual it's clearly stated that the array can be A multi-dimensional array or an array of objects from which to pull a column of values from. So it can be a multi-dimensional, not a strictly two-dimensional array... Why doesn't it work in my case though? What am I missing?
What I thought was that the multi-dimensional array cannot be an associative array, so to temporarily drop the date keys, I changed the above to:
array_multisort(array_map('strtotime', array_keys($program)), SORT_ASC, array_column(array_values($program), 'time'), SORT_ASC, $program);
but unfortunately this didn't work either...
I'm struggling to do that in a smart/elegant way and avoid using a loop to go through each value, but I ran out of ideas. So any help will be very much appreciated. TIA.
OK, I found it!!! I needed to iterate through each sub-array (by reference) of the initial array, and perform an array_multisort in there... So the code below did the trick, and I suppose it's as elegant as it can get!!!
array_multisort(array_map('strtotime', array_keys($program)), SORT_ASC, $program);
foreach ($program as &$day) {
array_multisort(array_column($day, 'time'), SORT_ASC, $day);
}