PHP array_multisort没有正确排序第二个数组

Question

Here is my code:

$numbers = array(10, 100, 100, 0);
$names = array("Alex", "Jane", "Amanda", "Debra");
array_multisort($numbers, $names);

print_r($numbers);
print_r($names);

The above code outputs:

Array
(
  [0] => 0
  [1] => 10
  [2] => 100
  [3] => 100
)

Array
(
  [0] => Debra
  [1] => Alex
  [2] => Amanda
  [3] => Jane
)

Why is the sorting of second array incorrect? If it is correct, could anyone explain how is it correct?

Thanks.

Answer 1

Yes, it is correct. You are taking PHP's 'array_multisort' function in wrong way. It will not sort both arrays, but will sort the first array and the second array will have positioning in order corresponding to first array.

$numbers Before sort:

(
  [0] => 10
  [1] => 100
  [2] => 100
  [3] => 0
)

After sort:

(
  [0] => 0 (position before sorting - 3rd)
  [1] => 10 (position before sorting - 0)
  [2] => 100 (position before sorting - 2 or 1)
  [3] => 100 (position before sorting - 2 or 1)
)

So, the second array will not get sort but will get its elements positioned according to first array.

(
  [0] => Debra --in first array 3rd element has moved to 0th position
  [1] => Alex -- in first array 0th element has moved to 1st position
  [2] => Amanda -- in first array 2nd element has moved to 2nd position
  [3] => Jane -- in first array 1st element has moved to 3rd position
)