how can use filter in php7.2 code example

Example: how can use filter in php7.2

Odd :
Array
(
    [a] => 1
    [c] => 3
    [e] => 5
)
Even:
Array
(
    [0] => 6
    [2] => 9
    [4] => 10
    [6] => 12
)