Question

I am trying to sort the arrays (each containing 2 date values) in a multidimensional array. I was able to find a useful function which solves the question for one element, however I was unable to modify it for two.

PHP Sort a multidimensional array by element containing date

function date_compare($a, $b)
{
    $t1 = strtotime($a['datetime']);
    $t2 = strtotime($b['datetime']);
    return $t1 - $t2;
}    
usort($array, 'date_compare');

The problem at hand is sorting comments in which have a post time and an edit time. Essentially I want to sort them from newest to oldest (while keeping both values).

If this is not possible, let me know.

EDIT: Mockup

$array = array(
    [0] => array(
          [0] => "Aug:1:2012 12:00:pm", // post date
          [1] => "Aug:28:2012 12:00:pm"  // edit date
    ),
    [1] => array(
          [0] => "Aug:1:2012 12:00:pm",
          [1] => "Aug:30:2012 12:00:pm"
    )
    [2] => array(
          [0] => "Aug:29:2012 12:00:pm",
          [1] => "Aug:1:2012 12:00:pm"
    )
};

Should output: $array[1] first (because it has the highest date out of keys 1 & 2) then $array[2], then $array[0].

$array = array(
    [0] => array(
          [0] => "Aug:1:2012 12:00:pm",
          [1] => "Aug:30:2012 12:00:pm" // highest   
    ),
    [1] => array(
          [0] => "Aug:29:2012 12:00:pm", // next
          [1] => "Aug:1:2012 12:00:pm"
    )
    [2] => array(
          [0] => "Aug:1:2012 12:00:pm",
          [1] => "Aug:28:2012 12:00:pm" // lowest
    )
};

Answer 1

I’m not sure if understood correctly but you mean you want sort your array base on column1 (“post date”) and if these values are equal order is determined by column2. So, what you need is just fix your comparing function:

function date_compare($a, $b)
{
    $t1 = strtotime($a['datetime']);
    $t2 = strtotime($b['datetime']);
    if ($t1 != $t2) {
        return $t1 - $t2;
    }

    // if "post dates" are equal, compare "edit dates"
    $t1 = strtotime($a['datetime2']);
    $t2 = strtotime($b['datetime2']);

    return $t1 - $t2;
}    

edit:

ok, according to your comment, you just need to pick up max element from your array. So, this should work:

usort($array, function($a, $b) {
    $t1 = max(strtotime($a[0]), strtotime($a[1]));
    $t2 = max(strtotime($b[0]), strtotime($b[1]));

    return $t1 - $t2;
});