Replace recursively only empty array values

Hey fellow coders, i need your assistance! (please send help)

lets say i got array A and array B:

A = [
'personal_data' => [ A => ['test' => A]],
'family_data' => [ A => ['test' => A]],
];

B = [
'personal_data' => '',
'family_data' => [ B => ['test' => B]],
'payment_info' => []
];

i got to replace the data from array A with array B having a preference over array A. (need to replace A with B:
if keys don't exist add them
if key exists and value differs replace value
if key exists and value does not differ do nothing)

i.e:

A = [
'personal_data' => '',
'family_data' => [
A => ['test' => A]
B => ['test' => B]
],
'payment_info' => []
];