CFS () -> save with multiple select

Hello
? CFS () -> save
I’m trying to save multiple select using, but I can not register well.
How can it be realized?

We are currently processing as follows, but only one value is registered.

$ select = [‘A’, ‘B’];

foreach ($ select as $ val) {
???????? $ field_data = array ($ key => $ val);
???????? $ post_data = array (‘ID’ => $ post-> ID);
???????? CFS () -> save ($ field_data, $ post_data);
}

Only ‘B’ is registered.