On Thu, 18 Apr 2002 12:36:13 +0200, Stig S. Bakken wrote:
>> Except that PEAR doesn't: no total encapsulation, returning different
>> types from the same method... That's not 'standard' OO, if there ever
>> was such a standard.
>
> PHP is not Java, C++, Python or Smalltalk. Designing PHP code like you
> would with Java will make your application horribly slow. PHP is
> loosely typed, Java has method overloading. Having different types in
> parameters and return values makes perfect sense in PHP, because that's
> what the language is designed for.
I agree that you should use a language's possibilities if that makes
sense. For example, I have written an object factory system in PHP that
allows dynamic addition of new classes: programmers drop a class in a
directory and give it an alias (e.g. 'foo'), after which the system is able
to create an object of that class, given its alias. It does that something
like this:
$class = includeClass('foo');
$object = new $class();
The 'new $class()' statement is very specific for PHP, and very useful.
On the other hand, I also think every language has 'features' that
shouldn't be used. Java and C++ (for example) both support public member
variables. That doesn't mean you should use them though. C++ has operator
overloading, which is often misused. Multiple inheritance can be nice,
but when used it mostly implies a bad design.
Although passing different types in parameters and returning different
types from methods is possible in PHP, I think there is absolutely no
justification for actually doing it. It only makes code much harder to
read, understand and use. Especially when returning different types from
the same method or function.
But of course I can be wrong, so please convince me otherwise; I'd really
like to hear your arguments. (But a warning in advance: I don't think the
PEAR error handling is a good example...)
> There are general OO principles, and there are techniques that are
> useful and common in specific languages. I have a feeling that what you
> refer to as 'standard' OO is a set of rules that make perfect sense for
> other languages, but not necessarily PHP.
On the contrary, my personal set of 'standard' OO principles tend to be
'cross-language'. Basically, I mainly use Design Patterns (Gamma, Helm,
Johnson, Vlissides) and Refactoring (Fowler) to implement my OO programs.
(Note: this is very, very basic!) I found that those techniques work
equally wel in any OO-enabled language.
Of course it is important to take the notions and quirks of the language
you're working in into account, but I also think that if a
'cross-language' solution to some problem is available at the same or
only a slightly higher cost - which is almost always the case - you should
always go for that.
Vincent
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