function loginall($username, $password)
{
    $db_host="localhost";
    $db_username="root";
    $db_password="";
    $db_name="name";
    $con=mysqli_connect($db_host, $db_username,$db_password, $db_name);
    $mysqli = new mysqli("$db_host","$db_username","$db_password", "$db_name");

    $qry = "SELECT username, password, level, active FROM businesses  WHERE username=? AND password=?
    UNION SELECT username, password, level, active FROM employees WHERE username=? AND password=?";
    $stmt = $mysqli->prepare($qry);
    $stmt->bind_param("ssss", $u,$p,$uu,$pp);
    $u = $username;
    $p = $password;
    $uu = $username;
    $pp = $password;
    $stmt->execute();
    $result = $stmt->get_result();
    while($row = $result->fetch_array(MYSQLI_ASSOC))
    {
        return $row;
    }
}

if(!($stmt=$mysqli->prepare($qry))){
    return ["Prepare failed: ".mysqli_error($mysqli)];  // what does this say?
}elseif(!$stmt->bind_param("ssss",$u,$p,$uu,$pp)){
    return ["Binding parameters failed: (" . $stmt->errno . ") " . $stmt->error];
}else{
    $u = $username;
    $p = $password;
    $uu = $username;
    $pp = $password;
    if (!$stmt->execute()){
        return ["Execute failed: (" . $stmt->errno . ") " . $stmt->error];
    }else{
        $result = $stmt->get_result();
        while($row = $result->fetch_array(MYSQLI_ASSOC)){
            $rows[]=$row;
        }
        return $rows;
    }
}

.....
...
.
$stmt->bind_param("ssss", $username, $password, $username, $password);
$stmt->execute();
$stmt->store_result();
$numRows = $stmt->num_rows;
$stmt->bind_result($usernameRow, $passwordRow, $levelRow, $activeRow);
if($numRows > 0) {
  while ($stmt->fetch()) {
    $u[] = $usernameRow;
    $p[] = $passwordRow;
    $uu[] = $levelRow;
    $pp[] = $activeRow;
  }
}
$stmt->close();