Error messages & can't reach admin after upgrading to 3.4.1 WordPress

The debug mode is on on your site. Go into wp-config.php and look for:

define( 'WP_DEBUG', TRUE );

Change TRUE to FALSE.

See Debugging in WordPress for more information.

If this doesn’t help the error_reporting level is set somewhere else.

.htaccess: Look for …
```
php_value error_reporting integer
```
… where integer matches one of the error constants. Remove the line or set its value to 1. More information.
Theme: Somewhere in your theme might be a line like this:
```
error_reporting( E_ALL | E_STRICT );
```
Remove that line. If you cannot find it, remove all themes, upload a fresh copy of TwentyEleven. WordPress will pick this up if there are no other themes available.
Plugin: One of your plugins can set error_reporting() too. Rename the directories plugins and mu-plugins in your wp-content directory to disable all plugins. If that fixes the problem download both directories and search for the error_reporting directive.
Drop-In: There is a number of files that are loaded automatically. Look in your wp-content directory for advanced-cache.php, db.php, db-error.php, object-cache.php and sunrise.php ([more information about that][5]).
Look also for a file in your languages directory named like en_US.php or de_DE.php. These are auto-loaded too.

If you still see no change the error_reporting is set in your php.ini. Ask your web hoster how to proceed.