If I understand correctly you can do it like the following, but it is an XY problem, why are you not structuring your arrays properly first?
$normalised = [];
foreach ($array as $key => $value) {
list($k, $a) = explode('-', $key, 2);
$normalised[$k][$a] = $value;
}
4
solved split an array into multiple part based on key pattern [duplicate]