a = A, b = B, c = c
a = A, b = B, c = c
a = A, b = C, c = c
array(2) {
  [0]=>
  string(1) "A"
  [1]=>
  string(1) "C"
}
a = D, b = b, c = c
a = C, b = A, c = c

a = A, b = B, c = c
a = A, b = B, c = c
a = A, b = C, c = c
array(2) {
  [0]=>
  string(1) "A"
  [1]=>
  string(1) "C"
}
a = D, b = b, c = c
a = C, b = A, c = c