It can happen that a faulty plugin breaks your WordPress site. Even worse, depending on how serious the error is, you can end up being unable to access the admin area where you would have been able to deactivate the WordPress plugin causing the error.
In that case, the best thing to do is to deactivate all plugins using the following SQL query:
UPDATE wp_options SET option_value = '' WHERE option_name = 'active_plugins';Most likely, this will solve the error and allow you to log back into your WP dashboard. Then you can re-activate the plugins one by one and identify which one was causing problems.