Hi,
On Wednesday 20 December 2006 13:37, Roman Neuhauser wrote:
> # zorglub_olsen@xxxxxxxxxxx / 2006-12-19 19:05:23 +0100:
>> I'm writing a PHP program and I've got a number of concerns. The program
>> is about 20 KLOC at the moment, but will probably grow quite a lot.
>>
>> I'm using OOP throughout, and I don't really have a lot of problems with
>> what PHP4 can do with OOP. PHP5 does have a nice feature or two,
>> eventhough none seems essential to my particular style of programming. I
>> don't mind using what PHP5 offers where it makes sense, but where's that?
>> Exceptions and new OOP features?
>>
>> Exceptions: I just don't see the big advantage. I've got errors and
>> messages bubbling up through object layers as it is, and exchanging that
>> with a wholly new structure seems more trouble that it's worth. I've read
>> several books on how cool PHP5 is, but the arguments for using exceptions
>> seem to boil down to "Java has them". Nowhere have I seen good examples
>> that really show how well exceptions solve real problems, all examples
>> seem to show are that 5 lines of try/catch are somehow sexier than 5
>> lines of if/else.
>
> One of the differences is that the if/else lines need to be in all layers
> between where the error might happen and where it will be ultimately
> handled. With exceptions, the try/catch can be detached (as long as it's
> the right thing to do, of course).
>
You're right, that is an advantage. I'll need to rewrite much of my current
code to make use of it, so that's not a high priority. More importantly I
have to start thinking in this new way to use exceptions properly.
>> What about performance?
>
> Did you measure the performance impact of all those if/else's?
>
> Exceptions are a special channel for errors, so your question is kind of
> like "is stderr any good? what about performance?"
>
If two different ways of doing the same thing seem very similar, performance
may help me choose. It's true that I don't know anything about the speed of
all my nested if/elses, but that's not necessarily relevant if others can
tell me that exceptions are always hopelessly slow.
>> New OOP features: I can go through my code and mark all my methods as
>> public or private or whatever. No problem. But why would I? It will make
>> classes easier to understand when I look at them, but that's just
>> convenience. What are the performance benefits? I've not found a single
>> mention of that anywhere. What do abstractions and interfaces actually
>> do, aside from structuring my code better?
>
> What do PHP4 classes actually do for you, aside from structuring your
> code? What about performance? Wouldn't you be better off if you wrote all
> of your program into a single file, all in global scope, using only
> builtin functions
> and primitive data types? It would surely be faster, and you'd only lose
> the convenience, no?
>
I get your point, everything above assembler on the metal can be
considered "merely convenience". In this case, however, there's a detail to
my question: I'm basically asking whether adding public/private to methods
will enhance performance. I could be -- I don't know about these things --
that the PHP processor could use such keywords to optimize the execution.
>> What major compelling reasons do I have to start using exceptions and
>> OOP-5?
>
> All the things you mentioned, and then some.
>
> Someone else mentioned that PHP 5 is much less inclined to copy objects.
> You still don't get the convenience of a private copy constructor, but
> hey.
>
> Another thing is destructors, so you're able to mimic C++'s powerful
>
> // unlocked
> {
> mylock_t lock;
> // locked
> }
> // unlocked
>
> (not so powerful in PHP without anonymous scopes).
>
> For example, a unit-testing library for PHP 5 called Testilence provides
> two utility classes, a temporary dir and a temporary file (see mkdtemp(3),
> mkstemp(3)). Both classes remove the underlying filesystem objects in
> their destructors, so you can conveniently skip doing the cleanup
> yourself:
>
> function test_O_EXCL_ThrowsOnExistingPath()
> {
> $file = $this->mkstemp();
> $this->willThrow('RuntimeException');
> new SplFileObject($file->path(), 'x+');
> }
>
> Also, notice how the code can omit checking for errors in mkstemp().
> The return value is guarranteed to be the right thing, since any errors
> would be signalled by throwing an exception, and that is handled By the
> caller of this method.
>
That looks interesting, thanks.
> How about iterators? You can have objects that look like arrays yet they
> take much less memory:
>
> $rs = $db->query($select); # query the db
> foreach ($rs as $row) { # fetch the row
> whatever($row);
> }
>
"takes much less memory" is exactly the kind of advice I'm looking for. I've
found very few usable guides to such optimizations. Could you possibly give
me a specific example of an array and a similar object with this great
difference in memory consumptions?
Thank you for your answer,
Niels
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