#20760 : is it really the intended behavior ?

Hi internals,

Trying to close some documentation bugs, I saw #20760.
Here's the problem :

class Foo {
var $bla;

function quux() {
$this->bla = 5;
}
}

class Bar {
var $bla;

function do_stuff() {
$this->bla = 10;
Foo::quux();
echo $this->bla;
}
}

$blabla = new Bar;
$blabla->do_stuff(); // will print 5, Foo::$bar value

Derick claimed that it was an intended behavior, I'd like to
make sure before documenting it. I'd also like to know why
do we have this feature ? It's quiet confusing.

Thank you in advance,

Mehdi Achour