It is not an error. That is just a
notice, kind of "warning". It is because the php.ini settings in you local machine is set to show you notices, along with
You could check if that value has been
set, in order to avoid that notice.
To do that, you can use
isset() function in PHP determines whether a variable is set and is not NULL. It returns a Boolean value, that is, if the variable is set it will return true and if the variable value is null it will return false.
To hide notices:
Now you have a
error_reporting set to include
E_NOTICE. You can choose not to show notices by setting
E_ALL & ~E_NOTICE