在页面呈现期间进行一次插入

我目前正在研究一个代码，可以在任何事情发生之前进行基本输入。这样它就可以将一些东西插入数据库，以便我可以提取该 ID 并插入该 ID 上。这将创建自动保存类型的插入。

以确保正确提交信息，并发现自己在呈现和输入方面遇到问题，因为呈现将导致插入被调用两次，而不是重定向页面。知道我如何让这个插入调用一次，并使代码按预期运行吗？

    /*
        NEW RECORD
    */
    // if the 'id' variable is not set in the URL, we must be creating a new record
    else
    {
                // insert null into database to create the save point
                if ($stmt = $mysqli->prepare("INSERT INTO test_table (name, email, notes) VALUES ('x', 'x', 'x')"))
                {
                    $stmt->execute();
                    $stmt->close();
                }
                // show an error if the query has an error
                else
                {
                    echo "ERROR: Could not prepare Auto-Save SQL statement.";
                }
                // gets id of null insert to update upon.
                $as_id = $mysqli->insert_id;
                printf ($as_id);
        // if the form's submit button is clicked, we need to process the form
        if (isset($_POST['submit']))
        {
            // get the form data
            $name = htmlentities($_POST['name'], ENT_QUOTES);
            $email = htmlentities($_POST['email'], ENT_QUOTES);
            $notes = htmlentities($_POST['notes'], ENT_QUOTES);
            // check that name, email are not empty.
            if ($name == '' || $email == '')
            {
                // if they are empty, show an error message and display the form
                $error = 'ERROR: Please fill in all required fields!';
                renderForm($name, $email, $notes, $error);
            }
            else
            {
                // insert the new record into the database
                if ($stmt = $mysqli->prepare("UPDATE test_table SET name=?, email=?, notes=? WHERE id=?"))
                {
                    $stmt->bind_param("ssss", $name, $email, $notes, $as_id);
                    $stmt->execute();
                    $stmt->close();
                }
                // show an error if the query has an error
                else
                {
                    echo "ERROR: Could not prepare SQL statement.";
                }
                // redirect the user
                header("Location: view.php");
            }           
        }
        // if the form hasn't been submitted yet, show the form
        else
        {
            renderForm();
        }
    }
    // close the mysqli connection
    $mysqli->close();
?>