Is it valid to re-declare or override an instance variable through inheritance?

[al-btar]

I have an abstract ParentClass with an \[code\]protected $instanceVariable\[/code\]. Now there's a \[code\]ChildClass\[/code\] which has also an \[code\]private $instanceVariable\[/code\]. It sets that to an initial value, like:\[code\]private $instanceVariable = 5;\[/code\]So the child class overrides it and changes the visibility to private. The parent class does not assign a value to that instance variable. It's also declared in the parent class because there are methods that access it.Is this just fine with PHP?