Edward Kay wrote:
Hi Richard,
This is very strange. I can certainly reproduce the problem. Putting a
var_dump($this) in ClassA's save method shows that PHP sees $this as an
instance of ClassB - when it should be of ClassA.
what *you* think it should be and what php's developers decided
it should be
about 3+ years ago obviously differ.
if you have an instance of ClassB it is exactly that - refering to $this
in the parent class definition won't magically make the class of
the instance change.
$this is plain this and not something else.
Yes, you are indeed correct.
I was thinking that as B extends A, A wouldn't know anything about B thus
$this in A would refer to A. I can now see that my logic was flawed here.
Thanks for pointing it out Jochem!
Richard, replacing your
if ($this->exists($value))
with
if (self::exists($value))
will call A's exists method, as you require. As Brad pointed out however,
your defintion of B overrides A's exists method. If you need both, then you
should rename the method in class B.
Edward
Using the self::exists(...) call instead of $this->exists(...) worked
perfectly. It threw me for a loop to see ClassA call a method in ClassB
even though ClassA has no reference to ClassB at design time. It is
probably why in other languages like C++ they use the virtual keyword to
identify this behaviour.
Can self::method(...)/self::$variable replace
$this->method(...)/$this->variable in all uses or are there cases where
you would need to use $this instead of self?
In another post Roman said that all non-private method are virtual in
PHP. If this is the case, I am assuming that the PHP architects would
want developers to use self:: in classes that could be subclassed with
method names that are the same as the parent(s)?
Thanks all for the help.
--
Richard Morris
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