Resolve PHP notice : check empty var

Resolve php notice on index :
Notice: Undefined index: user in /var/www/dropplets/settings.php on line 82
Check var with !empty() function
Notice fix : define() with a no existing var

Notice fix with a check of $login_error exist with !empty() :
Notice: Undefined variable: login_error in /var/www/dropplets/functions.php on line 110
Notice fix : check existance of var

Notice fix with a check of $options["category"]) with !empty(). Message of notice : Notice: Undefined index: category in /var/www/dropplets/functions.php on line 149
Notice fix : use the php function for get lenght of array

Replace .length with count() function, who work on php
Notice message : Notice: Use of undefined constant length - assumed 'length' in /var/www/dropplets/functions.php on line 160