Im so tired of finding the way to sort this multidimensional array. I have tried usort() but it doesnt sort the way I want to. Or just maybe I could not figure out the correct logic to use. usort() seems hard to understand for me.
I wanted to sort my data(example below), by finding first which has the higher value (between keys a and b) for each of the sub arrays. And then the sub array which has the highest value either from its keys a or b will be on top.
For example this array:
Array
(
[0] => Array
(
[a]=>5
[b]=>
[c]=>apple
)
[1] => Array
(
[a]=>5
[b]=>7
[c]=>guava
)
[2] => Array
(
[a]=>6
[b]=>
[c]=>banana
)
[3] => Array
(
[a]=>5
[b]=>
[c]=>avocado
)
)
should be sorted like this:
Array
(
[0] => Array
(
[a]=>5
[b]=>7
[c]=>guava
)
[1] => Array
(
[a]=>6
[b]=>
[c]=>banana
)
[2] => Array
(
[a]=>5
[b]=>
[c]=>apple
)
[3] => Array
(
[a]=>5
[b]=>
[c]=>avocado
)
So how exactly I am able to do this? Im so confused how to use usort. What is the best PHP function for sorting this?
Your comparison function:
function cmp($a,$b){
// clean up the keys so they don't cause weird cross-type comparisons
(empty($a['a']) ? $a['a'] = 0 : NULL;
(empty($a['b']) ? $a['b'] = 0 : NULL;
(empty($b['a']) ? $b['a'] = 0 : NULL;
(empty($b['b']) ? $b['b'] = 0 : NULL;
/// figure out the pertinent value to compare
$value_from_a_to_compare = max($a['a'],$a['b']);
$value_from_b_to_compare = max($b['a'],$b['b']);
if($value_from_a_to_compare == $value_from_b_to_compare) {
return 0;
}
if($value_from_a_to_compare > $value_from_b_to_compare) {
return 1;
} else {
return -1;
}
}
Call this from usort
usort($your_array,'cmp');
var_dump($your_array);
There are several methods, including writing the function written by dethtron5000 that would enable you to use usort.
I will describe a different suggestion: create a secondary array, in which you put the highest numbers from the first array and then use array_multisort to sort both, using the values from the secondary array.
$helper = array();
foreach ($data as $value)
{
$helper[] = max($value['a'],$value['b']);
}
array_multisort($helper,$data);
The way usort() works is that it requires a way to compare the elements of the array to each other to decide what comes first. You provide it a function, and it calls that function for each element pair in the input array. If the function returns a negative value, it means the first argument is less than the second argument and should come before it in the sorted array. The opposite is true if it returns a positive value.
Let's say you're comparing two sub-arrays s1 and s2. Using the logic you provided, s1 is "less than" s2 -- that is, s1 should come before s2 -- if max(s1.a,s1.b) > max(s2.a,s2.b). Thus, the sort function should return a negative value if this is true. If you subtract s1's max from s2's max, this should yield the proper result.
Try this:
function sort_function(array $arr1, array $arr2) {
$arr1_val = max($arr1['a'],$arr1['b']);
$arr2_val = max($arr2['a'],$arr2['b']);
return $arr2_val - $arr1_val;
}
usort($arr,sort_function);
Assuming $arr is your array.