Update to PHP standard
Update to PHP standard

* Remove the variables thrown into quotes, to be consistent
* Explicitly declare method visibility
* Update all calls to `__construct`
* Remove closing PHP tags
GenericSnake/interactive-tutorials,ubear/interactive-tutorials,ubear/interactive-tutorials,revzim/interactive-tutorials,GenericSnake/interactive-tutorials,ubear/interactive-tutorials,revzim/interactive-tutorials,revzim/interactive-tutorials,like9729/interactive-tutorials,revzim/interactive-tutorials,like9729/interactive-tutorials,daftano/interactive-tutorials,daftano/interactive-tutorials,ubear/interactive-tutorials,daftano/interactive-tutorials,daftano/interactive-tutorials,like9729/interactive-tutorials,ronreiter/interactive-tutorials,like9729/interactive-tutorials,GenericSnake/interactive-tutorials,ronreiter/interactive-tutorials,ronreiter/interactive-tutorials