Code Inspection: Undefined variable
Produces two types of warnings:
Undefined variable: the variable's definition is not found in the built-in library and project files.
Variable might have not been defined: there are one or more paths to reach the line with the variable usage without defining it.
All variables in the files that contain the
require statements are considered defined if the Ignore 'include' and 'require' statements option below is disabled.
By default, the inspection is enabled for global space. See global space (php.net) for details.