problem description
I wonder why an one-dimensional array becomes Boolean after experiencing walk. Ask the boss who knows to help solve the doubt.
related codes
public function test(){
        $arr = ["20181102","20181103","20181104","20181105","20181106","20181107"];
        $arr = array_walk($arr,function($item){
            $item = date_format(date_create($item),"m-d");
        });
        var_dump($arr);
        exit;
    }
in fact, what I expect is that the date is formatted as "month-day".
