At 17:04 19/08/2010, Ionut G. Stan wrote:
class Parent
{
public function foo(Foo $foo)
{}
}
class Child
{
public function foo(Bar $bar)
{}
}
class Foo
{}
class Bar extends Foo
{}
All fine until here, but what if...
class Taz extends Foo.
{}
I can't call Child::foo() with an instance of Taz, but I can call
Parent::foo() with such an instance. So, I can't use instances of
Child wherever instances of Parent would be accepted.
Child should clearly not be allowed to inherit Parent in the code
above, since the signature of Child::foo() is more restrictive than
the signature of Parent::foo(). The other way around could work
(although I don't recall if we allow it):
class Foo {}
class Bar extends Foo {}
class Parent
{
public function foo(Bar $bar){}
}
class Child extends Parent
{
public function foo(Foo $foo){}
}
No issues here - since any Bar object is also a Foo object and would
pass the is_a validation of Foo. Again, I don't recall if we allow
such signature overrides or not.
Zeev
--
PHP Internals - PHP Runtime Development Mailing List
To unsubscribe, visit: http://www.php.net/unsub.php
