How to sort multidimensional array by name/timestamp? [duplicate] - php

Question

This question already has answers here:
How can I sort arrays and data in PHP?
(14 answers)
Closed 5 years ago.
I were using the "rsort" function to sort through the timestamps when the array only contained a timestamp and were not multidimensional.
So now the question is how do i approach this?
The array looks something similair to this
Array
(
[0] => Array
(
[type] => post
[id] => 1
[timestamp] => 2017-08-12 21:03:22
[poster] => 1
[profile] => 1
[post] => Testtttttinngggs
)
[1] => Array
(
[type] => post
[id] => 2
[timestamp] => 2017-08-12 21:03:18
[poster] => 1
[profile] => 5
[post] => Hello you
)
[2] => Array
(
[type] => post
[id] => 3
[timestamp] => 2017-08-12 21:03:33
[poster] => 1
[profile] => 1
[post] => Somesay timestamp is screwed
)
[3] => Array
(
[type] => post
[id] => 4
[timestamp] => 2017-08-12 21:28:54
[poster] => 1
[profile] => 1
[post] => This is truely a teeest
)
[4] => Array
(
[type] => post
[id] => 5
[timestamp] => 2017-08-13 15:04:34
[poster] => 1
[profile] => 1
[post] => Test test test test
)
)

Answer 1

You can use array_multisort
array_multisort(array_column($list, 'timestamp'), SORT_ASC, $list);

Answer 2

You can use usort
usort($array, function($a, $b)
{
if($a['timestamp']>$b['timestamp'])
{
return -1;
}
elseif($a['timestamp']<$b['timestamp'])
{
return 1;
}
return 0;
});

Answer 3

Update
I was wrong. Axalix' answer runs a lot faster than mine and Rob Ruchte's. My tests:
$data = [
['timestamp'=> '2015-08-12', 'id'=>1],
['timestamp'=> '2017-07-13', 'id'=>2],
['timestamp'=> '2017-01-12', 'id'=>3],
];
function useUsort($data){
usort($data,function($a,$b) {
return strtotime($b['timestamp']) - strtotime($a['timestamp']);
});
};
function useMultisort($data){
array_multisort(array_column($data, 'timestamp'), SORT_DESC, $data);
};
$start = microtime(true);
for($i=1;$i<=100000;$i++) useUsort($data);
$t1 = microtime(true);
for($i=1;$i<=100000;$i++) useMultisort($data);
$t2 = microtime(true);
echo "usort: ". round(($t1 - $start) * 1000) . " ms\n";
echo "array_multisort: ". round(($t2 - $t1) * 1000) . " ms\n";
My result:
usort: 2262 ms
array_multisort: 246 ms
Original answer
#Axalix' answer is nice but I would take a different approach. Because you only care about sorting by one field (timestamp), array_multisort is overkill as it was design to sort by multiple fields. I would do:
usort($data,function($a,$b) {
return strtotime($b['timestamp']) - strtotime($a['timestamp']);
});
Live demo
This will easily outperform array_multisort because it doesn't require PHP to first extract the timestamp into a separate column array, and then execute the multisort (a more complex function than my simple comparator function) on it.