PHP sort multidimensional array by date

Question

I'm having a problem. I have a multidimensional array, that looks like this:

Array ( [0] => 
              Array ( 
                    [0] => Testguy2's post. 
                    [1] => testguy2 
                    [2] => 2013-04-03 
              ) 

        [1] => Array ( 
                    [0] => Testguy's post. 
                    [1] => testguy 
                    [2] => 2013-04-07 
              ) 
);

I want to sort the posts from the newest date to the oldest date, so it looks like this:

Array ( [1] => Array ( 
                     [0] => Testguy's post. 
                     [1] => testguy 
                     [2] => 2013-04-07 
               ) 
        [0] => Array ( 
                     [0] => Testguy2's post. 
                     [1] => testguy2 
                     [2] => 2013-04-03
               ) 
);

How do I sort it?

Answer 1

function cmp($a, $b){

    $a = strtotime($a[2]);
    $b = strtotime($b[2]);

    if ($a == $b) {
        return 0;
    }
    return ($a < $b) ? -1 : 1;
}

usort($array, "cmp");

Or for >= PHP 7

usort($array, function($a, $b){
    return strtotime($a[2]) <=> strtotime($b[2]);
});

Answer 2

You can do it using usort with a Closure :

usort($array, function($a, $b) {
    $a = strtotime($a[2]);
    $b = strtotime($b[2]);
    return (($a == $b) ? (0) : (($a > $b) ? (1) : (-1)));
});

Answer 3

I'm just stepping away from my desk for the day so I can't offer specifics. But here's a good place to get started that includes examples: array_multisort

Answer 4

$dates = array();       
foreach($a AS $val){
    $dates[] = strtotime($val[2]);
}
array_multisort($dates, SORT_ASC, $a);