How do one php array compare with another add the difference to the last one?

Question

PHP

Hello! Please tell me how to implement in php. There is an array $a (contains multiple values) and an array $b (empty). Compare $a with $b and add the difference to $b, then iterate until the array $b is completely filled with all elements from $a. Tried array_diff(), but it compares by values, not by keys

Answer 1

php.net/manual/en/ref.array.php
We see the array_diff_assoc function, try

Answer 2

I think array_merge will suit you