You can simply use foreach
instead like as
foreach($your_arr as &$v){
$v = [$v["period"] => $v["way"]];
}
print_r($your_arr);
Or using array_map
$your_arr = array_map(function($v){ return [$v["period"] => $v["way"]]; },$your_arr);
print_r($your_arr);
solved PHP Use array map to reOrder an array