PHP日期比较不正确

Question

I am modifying a custom feature within Joomla/K2, but it's really only PHP involved. This functionality isn't available via any modules or extensions so I really need to figure it out.

I am outputting K2 articles and trying to sort by a date field which is an 'Extra Field' in K2. It is stored in the database as a date string. My function to sort works, in that it changes the order of the items - but it does not work to get them in the correct sequence.

function cmp($a, $b){
    global $array;
    return strcmp($array[$a][1], $array[$b][1]);
}


  $limit = 3;
  $limitstart = 0;

  foreach($items as $key=>$item) {

            $extraval = NULL;

            foreach ($item->extra_fields as $extraField){
                if($extraField->value != ''){
                    if($extraField->name == "Start Date"){
                      $extraval = strtotime($extra_field->value);
                    }
                }
            }

            $extrasort[$key] = Array();
            $extrasort[$key][0] = $item;
            $extrasort[$key][1] = $extraval;

          }

          sort($extrasort, 'cmp');

          $rows = Array();
          $total = $limit + $limitstart;

          for($i=$limitstart; $i<$total; $i++) {
            if(!empty($extrasort[$i][0])) {
              $rows[] = $extrasort[$i][0];
            }
          }

The output from this currently is:

1381525200
1380834000
1386795600

Which is not correct, (hopefully) obviously.

Any suggestions at all or tips would be so appreciated, I have been playing with this for hours and in general I am unsure about the 2D array.

Thanks

Answer 1

The callback function that sort uses is provided the two values that need to be compared. There's no need to go looking at a global array. In this case, you're provided with the two elements in $extrasort, which are themselves arrays, so you just need to look at the elements you want to sort on.

Your function should (probably) be:

function cmp($a, $b){
 return strcmp($a[1], $b[1]);
}

Answer 2

Thanks for your help Mike. My solution was to convert the date into ISO (YYYY-MM-DD) format and sort using the function below:

function compareasc($v1, $v2) {
       if ($v1[1] == $v2[1]) return 0;
       return ($v1[1] < $v2[1])?-1:1;
}

usort($extrasort, 'compareasc');