uksort Sort an array by keys using a user-defined comparison function &reftitle.description; booluksort arrayarray callablecallback uksort will sort the keys of an array 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. ¬e.sort-unstable; &reftitle.parameters; array The input array. callback &return.callbacksort; &callback.cmp; &reftitle.returnvalues; &return.success; &reftitle.examples; 1, "the Earth" => 2, "an apple" => 3, "a banana" => 4); uksort($a, "cmp"); foreach ($a as $key => $value) { echo "$key: $value\n"; } ?> ]]> &example.outputs; &reftitle.seealso; usort &seealso.array.sorting;