The uksort() function is used to sort an array by the element keys using a user-defined comparison function. If the array you wish to sort needs to be sorted by some non-trivial criteria, you should use this function.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.uksort — Sort an array by keys using a user-defined comparison function.The uksort() function sorts an array by keys using a user-defined comparison function.