In PHP, the "Typed property must not be accessed before initialization" error is encountered when a property is defined with a type hint, but it is accessed before it has been explicitly assigned a value.
In Python, you can use the self keyword to refer to the instance of the enclosing class within a method.
In PHP7, nullable return types were introduced, allowing a function to return either a specific type or null.
In PHP 7, type hinting can be used to specify the expected data type of a function or method parameter.