Sorting a table in PHP

I have some difficulty sorting my array. It looks like this :

[0] => Array
        (
            [firstname] => Jnic
            [lastname] => Fortin
            [points] => Array
                (
                    [id] => 20453
                    [f] => 31
                    [r] => 7                 
                    [total] => 82
                )

        )

    [1] => Array
        (
            [firstname] => Kris
            [lastname] => Anders
            [points] => Array
                (
                    [id] => 20309                    
                    [f] => 0
                    [r] => 1
                    [total] => 56
                )

        )
[2] => Array
            (
                [firstname] => Em
                [lastname] => Zajo
                [points] => Array
                    (
                        [id] => 20339                    
                        [f] => 8
                        [r]开发者_开发问答 => 3
                        [total] => 254
                    )

            )

I would like to sort it by "total" DESC. How could I do it? If everything sort ok the array would be order [2][0][1] (254,82,56)

You probably can use the usort function for that : it sorts an array, using a callback function to compare the elements of that array :

bool usort  ( array &$array  , callback $cmp_function  )

This function will sort an array by its values using a user-supplied comparison function. If the array you wish to sort needs to be sorted by some non-trivial criteria, you should use this function

If your function is defined to compare per $element['points']['total'], it should do the trick.

Edit : And here is the example, using uasort, which is the same as usort, but will keep the array keys, like pointed out by ryanday :

First, let's declare the array :

$a = array(
    array(
        'firstname' => 'Jnic',
        'lastname' => 'Fortin',
        'points' => array(
            'id' => 20453,
            'f' => 31,
            'r' => 7,
            'total' => 82,
        ),
    ),
    array(
        'firstname' => 'Kris',
        'lastname' => 'Anders',
        'points' => array(
            'id' => 20309,
            'f' => 0,
            'r' => 1,
            'total' => 56,
        ),
    ),
    array(
        'firstname' => 'Em',
        'lastname' => 'Zajo',
        'points' => array(
            'id' => 20339,
            'f' => 8,
            'r' => 3,
            'total' => 254,
        ),
    ),
);

And then, the comparison function :

function my_compare($a, $b) {
    if ($a['points']['total'] > $b['points']['total']) {
        return -1;
    } else if ($a['points']['total'] < $b['points']['total']) {
        return 1;
    }
    return 0;
}

And, finally, we use it :

uasort($a, 'my_compare');
var_dump($a);

And get the array, sorted by total desc :

array
  2 => 
    array
      'firstname' => string 'Em' (length=2)
      'lastname' => string 'Zajo' (length=4)
      'points' => 
        array
          'id' => int 20339
          'f' => int 8
          'r' => int 3
          'total' => int 254
  0 => 
    array
      'firstname' => string 'Jnic' (length=4)
      'lastname' => string 'Fortin' (length=6)
      'points' => 
        array
          'id' => int 20453
          'f' => int 31
          'r' => int 7
          'total' => int 82
  1 => 
    array
      'firstname' => string 'Kris' (length=4)
      'lastname' => string 'Anders' (length=6)
      'points' => 
        array
          'id' => int 20309
          'f' => int 0
          'r' => int 1
          'total' => int 56

ryanday > Thanks for your answer !

You will want to use usort as answered by @Pascal MARTIN, but here is the full code to achieve what you want:

function total_sort($a, $b){
    $a_total = $a['points']['total'];
    $b_total = $b['points']['total'];

    if($a_total == $b_total) return 0;

    return ($a_total > $b_total) ? -1 : 1;
}

usort($array, "total_sort");

EDIT: After I posted I saw @Pascal updated his answer to include a sample. Since I wrote my sort function a little different, I am leaving it here as another reference.

usort is a robust solution that can be very flexible for complex cases. Since your data set is relatively simple i would suggest the following:

// assuming your array has been defined in $a
$sort = array();
foreach ($a as $key => $suba)
{
    // this collects the values you want to sort by and associates them with the correct index
    $sort[$key] = $suba['points']['total'];
}
// this sorts the collected values
sort($sort);

// this re-sorts $a according to the sorted $sort array
array_multisort($a, $sort);

not sure about performance but this is at least AS GOOD as usort if not better

I noticed you said the proper array should be ordered [2][0][1], if that index association is important to you follow Pascal's advice with the uasort() function.