Sorting a multidimensional associative array

[dcnguyen]

Argh...I swear I've read about 20 articles on usort, but can't find the answer to what must be a common dilemma:

I have an array that is formatted as such:

Array
(
    [0] => Array
        (
            [title] => Dog
            [2000] => 278
            [2007] => 50
       

        )

    [1] => Array
        (
            [title] => Cat
            [2000] => 41
            [2007] => 740
 

        )

    [2] => Array
        (
            [title] => Monkey
            [2000] => 378
            [2007] => 65
       

        )
)

And what I want to do is give the user some radio buttons so that they can pick which field to sort by, and also whether to do it ascending or descending. I understand how usort works, but in order to use it, I have to do something like:

function compar($a, $b) {
       return strnatcmp($a["title"], $b["title"]);
}

usort($array, 'compar');

How do I work with usort so I can enter in other variables that dictate by which attribute the array is sorted by, so I don't have to write a bunch of comparison functions and make different calls to usort?

 

[sleipnir214]

Assuming that the user's sort-column choice is submitted in $_POST['sort_column'] and sort direction in $_POST['sort_direction'] and that $_POST['sort_direction'] will contain 'ASC' for ascending and 'DESC' for descending sort order.

Then something like:

function compar($a, $b)
{
   $retval = 0;
   switch ($_POST['sort_column'])
   {
      case 'title':
         $retval = strnatcmp($a['title'], $b['title']);
         break;

      case '2000':
         $retval = strnatcmp($a['2000'], $b['2000']);
         break;

      //  Additional cases here
   }

   if ($_POST['sort_direction'] == 'DESC)
   {
      $retval *= -1;
   }

   return $retval;
}

usort($array, 'compar');

Might get you somewhere near where you want.



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[dcnguyen]

Thanks, that worked. Hoped for a built-in function, but whatever does the job.

 

[sleipnir214]

A sorting routine must take into account the datastructure on which it operates. How would the programmers of the PHP engine know about your user-defined datastructure?



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