php – I’m trying to fetch all data related to an column

What i’m trying to do is display every user_id row that is related to coupon_id 3

I was able to only display one user_id using the while loop

$query = "SELECT * from coupon_log WHERE coupon_id = 3 ";

$fetchname = mysqli_query($connection,$query);

while($row = mysqli_fetch_assoc($fetchname)){

    $username = $row('user_id');



}
echo $username;

Here’s how my table looks table

So basically I’m trying to display all user_id rows that is only related to row coupon_id 3 but so far i’m only displaying 1 user_id not all of them