Array divided into days of the week

Question

I want the array to be divided into days of the week according to the date specified in BETWEEN and AND

public static function showDataByEmployer($employer)
 {


    $sql = 'SELECT `WorkingDay` 
            FROM `status` 
            WHERE `WorkingDay` BETWEEN "2021-04-12" AND "2021-04-16" 
                   AND NameFinish = :employer ';

    $db = static::getDB();
    $stmt = $db->prepare($sql);
    $stmt->bindValue(':employer', $employer, PDO::PARAM_STR);
    
    $stmt->execute();
    $user_data = $stmt->fetchAll();

    print_r($user_data);
 }

What is the best way to display the data in an array by day of the week. My example :

Array
(
    [0] => Array 
        (
            [0] => Array
                (
                    [WorkingDay] => 2021-04-12 00:00:00
                    [0] => 2021-04-12 00:00:00
                )

            [1] => Array
                (
                    [WorkingDay] => 2021-04-12 00:00:00
                    [0] => 2021-04-12 00:00:00
                )

            [2] => Array
                (
                    [WorkingDay] => 2021-04-12 00:00:00
                    [0] => 2021-04-12 00:00:00
                )
        ) 
        
    [1]=> Array
        (
            [0] => Array
                (
                    [WorkingDay] => 2021-04-13 00:00:00
                    [0] => 2021-04-13 00:00:00
                )

            [1] => Array
                (
                    [WorkingDay] => 2021-04-13 00:00:00
                    [0] => 2021-04-13 00:00:00
                )

            [2] => Array
                (
                    [WorkingDay] => 2021-04-13 00:00:00
                    [0] => 2021-04-13 00:00:00
                )
        )      

)

Where [0] is monday 12-04, [1] is Tuesday 13-04 ect.