PHP: bool vs boolean type hinting

I've been trying to use type hinting more in PHP. Today I was writing a function that takes a boolean with a default parameter and I noticed that a function of the form

function foo(boolean $bar = false) {
    var_dump($bar);
}

actually throws a fatal error:

Default value for parameters with a class type hint can only be NULL

While a function of the similar form

function foo(bool $bar = false) {
    var_dump($bar);
}

does not. However, both

var_dump((bool) $bar);
var_dump((boolean) $bar);

give the exact same output

:boolean false

Why is this? Is this similar to the wrapper classes in Java?