The following program will return 0 whereas it should return 1 :

if (TRUE) {
  class titi {
    var $KEYS = array();
  }
  class toto extends titi {
    var $KEYS = array("login");
  }
}
$toto = new toto;
echo count($toto->KEYS);

Note that the problem disappears if you remove the if (TRUE) statement.