$sql_check_user_orders="select OrderID from tblorderdetails
  inner join CustomerID.tblcustomer=CustomerID.tblorderdetails
  where CustomerID.tblorderdetails='sql_get_user_id'$.tblcustomer";
  $qry_check_user_orders=mysqli_query($con ,$sql_check_user_orders);
  if(isset( $qry_check_user_orders)){
    $loginDate = date('dmYHs');
    $order_date = $qry_check_user_orders;
    $datediff = $loginDate - $qry_check_user_orders;

    $rent_period= ($datediff / (60 * 60 * 24));

    if($rent_period > 4)
      $sql_block_user="update `tblcustomer` set `blocked`='1' where CustomerID='$qry_get_user_id'"
      $qry_block_user=mysqli_query($con ,$sql_block_user);
    }