Fatal error: Missing function get_old_user()

Can you confirm that you have the User Switching plugin active when you active the Admin Bar User Switching plugin please.

Hi Mark, User Switching was not installed or activated, works a treat once User Switching was activated. ??

Consider using class_exists or function_exists before loading resources from another Plugin and an Admin notice prompt to install and activate User Switching if it’s not installed or activated.

The plugin does do exactly that:

https://github.com/wpmark/admin-bar-user-switching/blob/master/admin-bar-user-switching.php#L30-L55

Therefore not sure how it managed to bypass this!

Hi Mark, I assume (and this is a wild shot) that the wp_before_admin_bar_render Action runs before the admin_notices Action.

Update: Yup, that looks like the culprit, /wp-admin/admin-header.php #203

do_action( ‘in_admin_header’ );

followed by #239 26 lines later…

do_action( ‘admin_notices’ );

Adding another class_exists within abus_adminbar_output() that returns nothing should resolve this.

What you are saying makes sense. However I have just do the following:

1. Deactivated all plugins
2. Activate the Admin Bar User Switching Plugin – admin notice shows and plugin is deactivated because User Switching is not active
3. Activate User Switching
4. Activated Admin Bar User Switching
5. Deactivate User Switching – admin notices shows the error and the Admin Bar User Switching plugin is deactivated.

Therefore what I have in the plugin seems to be working in that if the User Switching plugin is not active the Admin Bar add-on won’t active and if the two are activated and User Switching is deactivated it deactivates the Admin bar one.

At no point do I see a fatal error.

Hi Mark, with both User Switching and Admin Bar User Switching activated I clicked de-activate on User Switching to see what would happen. I hit the fatal error and blank screen on WP Admin.

Adding…

if( ! class_exists( ‘user_switching’ ) )
return;

to line #110 of admin-bar-user-switching.php and refreshing the Plugin screen then showed the WP Admin screen with the de-activation notice you wrote. What I noticed however was that the Switch to User dropdown on the WP Admin bar was still visible, this is because is it rendered as part of the in_admin_header Action and so the Plugin is calling resources from User Switching without knowing that the Plugin has been de-activated and before the de-activation script you’ve written kicks in as part of admin_notices Action.

Here’s my version details:

WordPress 4.1.1
User Switching 1.0.3
User Switching in Admin Bar 1.0.3

Logged in as an Administration User Role

Thanks for your time looking at this with me

Happy to go ahead and apply that fix but I would like to be sure of why I am not seeing this and you are. Could you test this on another install please in the same environment making sure it a vanilla WP install with just the two required plugins?

I’ll do this tomorrow morning on one of my development sites and confirm here ??

Yup, same issue. Both scenario’s no Plugins activated, default Twenty Fifteen Theme.

=== Scenario 1 ===

Install Admin Bar User on new WordPress site without User Switching using the WordPress Plugins Installer.

Result: Fatal error on activation, can only be resolved by renaming/deleting Plugin directory for Admin Bar User Switching.

=== Scenario 2 ===

Install User Switching on new WordPress site and activate Plugin, then install and activate Admin Bar User Switching from WordPress Plugins Installer. Then de-activate Admin Bar User Switching from the Plugins screen.

Result: Fatal error on de-activation of Admin Bar User Switching, can only be resolved by renaming/deleting Plugin directory for Admin Bar User Switching.

I have now added a check in the admin bar output function to check for user switching being active. This should prevent your issue. Released in 1.0.4 a few minutes ago!

Works like magic ??

Excellent glad it works for you!