Sorting a table in PHP - php

Question

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] => 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)

Answer 1

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 !

Answer 2

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.

Answer 3

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

Answer 4

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.