Today one of my blogs had a problem with the admin area not working at all. The admin login page was just a white screen with no obvious fatal error.
Often, this will be due to some PHP code that is badly formed, but you would know this as soon as you implemented a change.
In my case, I hadn't changed anything, it just stopped working. The main site was fine, with the posts showing.
WordPress can obscure error messages from PHP due it redirecting pages, so in the wp-config file you can add the line of code:
Then this produces verbose messages about all that may be wrong with your plugins. But most of this will be just advice to stop using something that has been deprecated (to be phased out) or about something that is not up to coding standards etc.
So after doing this, switch this feature off with:
This didn't reveal my problem.
It can take a long time to diagnose this kind of problem as you can find via web searches where people say they spent hours trying to fix things.
The long-way is to insert die statements in the code to find out where it breaks by gradually homing in on the fail point.
But suspecting plugins, I removed them all via the database.
To do this, login to cpanel and go to phpmyadmin and find your WP database.
Then do a search on wp_options and look for the active plugins entry by using the search feature and searching for the option_name field called "active_plugins".
Then click on the pencil icon to edit this entry.
Cut and paste the option_value which contains all the active plugins. Clear this box and save (go back to previous page) with the "go" button.
Now there are no active plugins on your blog.
Refresh the wp-admin area in your browser. Still a white screen maybe.
Then repeat the exercise with the database edit by now pasting the plugin data back into the active_plugins option_value text box and saving it.
So now the active plugins are restored.
Then refresh the wp-admin area in your browser again and hopefully you get to see the admin login form and all will be well again.
This worked for me and just took a few minutes without needing to re-install stuff and spend hours online seeking advice.
So hopefully it works for you too but I can't provide any guarantees. I still don't know exactly what went wrong, and your situation may be entirely different.
Be careful not to lose the cut and paste plugin data, copy this to a text editor.