_SESSION in foreach

Question

我有简单的登录PDO MSSQL Server

if ($_SERVER['REQUEST_METHOD'] == 'POST') {
    $username = $_POST['user'];
    $password = $_POST['pass'];
    $hashedPass = passConvert($password);
    // Check If User Exits in Database
    $stmt = $con->prepare("   SELECT [UID]
      ,[ID]
      ,[PWD]
  FROM [kal_auth].[dbo].[Login] WHERE [ID] = '$username' AND [PWD] =$hashedPass  
                                       ");
    $stmt->execute();
    $row = $stmt->fetchAll(PDO::FETCH_ASSOC);
    $count = $stmt->rowCount();
    // IF COUNT > 0 This Mean Database Account About Username
    if ($count > 0) {
        foreach ($row as $rows){
            $_SESSION['ID'] = $rows['UID'];
            $_SESSION['Username'] = $rows['ID'];
        }
        header("location:test.php");
    }

}

我的问题是..在foreach循环中使_SESSION是安全的还是不安全？