Not update database value automatically

Question

I am facing a problem. I have made payment through paypal. After payment when it redirect to my website, i have a code which update the value in database. But when i refresh the same page, it automatically update its value. I only want to update value only on making a payment not on refreshing. I am using the code

$db  = JFactory::getDBO();
$result = null;     
$user    = JFactory::getUser();

if ($user->guest) {
    return false;
}

$query = 'SELECT credit' .
         'FROM #__vodes_credits' .
         'WHERE userid = ' . (int) $user->id;
$db->setQuery($query);
$result = $db->loadResult();

$result_final = $result+20;

$query = 'update #__vodes_credits SET credit='.$result_final.
         'WHERE userid = ' . (int) $user->id;
//echo $query;
$db->setQuery($query);

$result = $db->loadResult();
if ($db->getErrorNum()) {
    JError::raiseWarning( 500, $db->stderr());
}

return $result;

$app = JFactory::getApplication();
$app->redirect("localhost/Joomla/");

Please help me to sought it out.

Answer 1

Your code is fine until the last three lines. I am assuming this code is in the controller method whose name corresponds to the task parameter in the url paypal is invoking.

return $result;

$app = JFactory::getApplication();
$app->redirect("localhost/Joomla/");

You should not be returning the result. You're skipping the redirection part which is going to achieve your goal.

Once you parse the result of a sensitive form, it is good practice to redirect so any refresh / reload won't trigger the same actions again. But you're returning before the redirect is set.

Additionally, I don't think redirecting to "localhost/Joomla" really makes sense, usually you would redirect implicitly with setRedirect() to a view of your component where you show the payment details, and passing in a message to display to the user, just to let them know you processed the payment correctly.

To sum it up, your code should end with:

$app->setRedirect(JRoute::_("index.php?option=com_yourcomponent&view=paymentsuccess"),JText::_("HAPPY_PAYMENT_MESSAGE"));

with no returns;