Displaying error messages with PHP

Question

I want to display an error if a user tries to go to /admin/ when they aren't logged in as an admin. I don't want to pass stuff in the URL and I do not want to do a $_POST to display the error. I just want to display a message and when you refresh it is gone.

For example, go to this URL: http://getsatisfaction.com/getsatisfaction/topics/notifications_box/edit

It returns you back to the topic and says "I'm sorry, but you have been denied access to edit this topic."

When you refresh it is gone. I want to be able to display an error like that too. Does anyone know how they did that?

I've seen other sites do this as well (without appending an ?error=1 to the end of the URL).

Thanks in advance.

How are you currently logging someone in as admin? Cookies? Sessions? — j08691
– j08691, Commented Jan 5, 2012 at 22:42
Does your codebase currently support the separation of users based on roles? (i.e. admins vs normal users)? — Mike Purcell
– Mike Purcell, Commented Jan 5, 2012 at 22:47
@DigitalPrecision Yeah, I have a column in the database called "type" and that is either "admin" or "user". — Nathan
– Nathan, Commented Jan 5, 2012 at 22:48

deceze · Accepted Answer · 2012-01-05 22:45:43Z

2

Set the error message in the session:

session_start();
$_SESSION['message'] = 'No, you fool!';
header('Location: some-other-page.html');
exit;

Display the message:

session_start();
if (!empty($_SESSION['message'])) {
    echo $_SESSION['message'];
    unset($_SESSION['message']);
}

answered Jan 5, 2012 at 22:45

deceze♦

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2 Comments

Mike Purcell Over a year ago

This snippet is missing the check to determine if account is 'admin' or not, may want to add it for completeness.

Nathan Over a year ago

@DigitalPrecision Yeah, I already check to see if it is an admin. I just didn't know how to display error messages - I was just redirecting them to the homepage if they aren't an admin. Now I can display an error with it as well.

Nir Alfasi · Accepted Answer · 2012-01-05 22:46:04Z

1

You need to check the session and see if the user has permission. Checking the session is specific to the environment, for example, if you use Joomla: http://www.howtojoomla.net/how-tos/development/how-to-use-sessions-in-joomla

and if you use drupal: http://drupal.org/node/360542

of course that there's a native library for sessions in php: http://php.net/manual/en/ref.session.php

hope it helps!

answered Jan 5, 2012 at 22:46

Nir Alfasi

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3 Comments

Nathan Over a year ago

I already check if the user has permission and if the session has the correct variables. But right now, I'm just redirecting them back to the homepage if they aren't logged in and if they aren't an admin. Thanks for all the links, though :)

Nir Alfasi Over a year ago

Oh, I didn't understand your question... but now that I do: you can send yourself a parameter using $_POST instead of using $_GET - this way it will not be displayed on the address bar (as part of the URL) - why don't you want to use POST ? Another way is set a costumed session variable - that should do the trick

Mike Purcell Over a year ago

Session is definitely the way to go in this situation.

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