Redirect to landing page: header("Location:index.php");

Hi Guys trying to find the mistake page not changing to index.php.

Not Redirecting to landing page everything else works fine.

Record is deleted from db, page with delete yes/no also ok

        // Process delete operation after confirmation

    if(isset($_POST["ID"]) && !empty($_POST["ID"])){
        // Include config file
        require_once 'config.php';

        // Prepare a select statement
        $sql = "DELETE FROM cv WHERE ID = ?";

        if($stmt = mysqli_prepare($link,$sql)){
            // Bind variables to the prepared statement as parameters
            mysqli_stmt_bind_param($stmt, "i", $param_ID);


            // Set parameters
            $param_ID = trim($_POST["ID"]);

            // Attempt to execute the prepared statement
            if(mysqli_stmt_execute($stmt)){
                // Records deleted successfully. Redirect to landing page

                header('Location:index.php');
               exit;



            }else{
                echo "Oops! Something went wrong. Please try again later.";
            }
        }

        // Close statement
        mysqli_stmt_close($stmt);


        // Close connection
        mysqli_close($link);
    } else{
        // Check existence of ID parameter
        if(empty(trim($_GET["ID"]))){
            // URL doesn't contain ID parameter. Redirect to error page
            header("location: error.php");
            exit();
        }


    }
   ?>

Any help would be great.

Warning: Cannot modify header information - headers already sent by (output started at /storage/public_html/crudbd/config.php:31) in /storage/public_html/crudbd/delete.php on line 26