In drupal 7 , the error reporting settings in php.ini is overridden by the bootstrap sequence. Even you changed your site’s htaccess settings, it won’t work as drupal forces you to use E_ALL.
As result some modules may produce undefined variables that will be displayed as messages “Notice: Undefined index” or “Notice: Undefined variable” and your logs will grow insanely.
The quick solution is to add in your settings.php the following line:
ini_set('error_reporting', 'E_ALL ^ E_NOTICE');