Drupal - Filter a view based on current user's roles?

Following @Jimajamma's suggestion, here's what I used. I adapted his code slightly for Drupal 7 and to allow for other roles than Administrators full access to the results.

In the View, add a contextual filter on Author: Uid, and use the following settings:

WHEN THE FILTER VALUE IS NOT AVAILABLE:

• Provide default value
• Type: PHP Code

Use the following code:

global $user;

if (
    in_array('administrator', $user->roles) || 
    in_array('editor', $user->roles)
)
{return -1;}
else
{return $user->uid;}

WHEN THE FILTER VALUE IS AVAILABLE OR A DEFAULT IS PROVIDED

• Specify validation criteria
• Validator: PHP Code

Use the following code:

if ($argument == -1) 
{return FALSE;}
else
{return TRUE;}

• Action to take if filter value does not validate: Display all results for the specified field (this is what will give admins access to all results)

And that's it!

Notes:

Compared to my initial settings, the relationship (Content: Author) isn't needed anymore; neither is the "Author" filter (which was brought in by the relationship anyway).

Apparently, for Drupal 6 the condition in the first PHP snippet should rather be if (in_array('super user', array_values($user->roles))).

You need to add a Contextual Filter to filter based on the currently logged in user.

1. Add a contextual filter for "User: Uid"
2. Select "Provide a default value"
3. Choose Type: "User ID from logged in user"

You would also need to clone a new view display to show all nodes for specific roles, configured by Page Settings: Access > Role. Then choose Administrator and any other roles who should see all nodes.

You cannot OR a filter like a sort, and you would be displaying the view two different ways with filtered content and all content, so I would create two displays of this view.