How would you sort an array of strings to their natural case-insensitive order, while maintaing their original index association?

For example, the following array:

array(

                '0' => 'z1',

                '1' => 'Z10',

                '2' => 'z12',

                '3' => 'Z2',

                '4' => 'z3',

)

After sorting, should become:

array(

                '0' => 'z1',

                '3' => 'Z2',

                '4' => 'z3',

                '1' => 'Z10',

                '2' => 'z12',

)

The trick to solving this problem is to use three special flags with the standard asort() library function:

asort($arr, SORT_STRING|SORT_FLAG_CASE|SORT_NATURAL)

The function asort() is a variant of the standard function sort() that preserves the index association. The three flags used above SORT_STRING, SORT_FLAG_CASE and SORT_NATURAL forces the sort function to treat the items as strings, sort in a case-insensitive way and maintain natural order respectively.

Note: Using the natcasesort() function would not be a correct answer, since it would not maintain the original index association of the elements of the array.