[RESOLVED] Some class and framework things

Desdinova

Hi, I'm new. :o Hope you guys can help me out here.

I'm working with classes since a couple of weeks now, after programming without classes for about 2.5 year. Basically this means I have quite a structure for using non-OOP, and lack structure for OOP.

I work with PHP 4.4 for now.

My problem;

I often like to create structures that require a lot of classes. much like a spider in the web, the spider being the core. So from that core, I'd like the ability to reach every other class I have created. Of course, I can initiate every class every time I'd like. But take this for example;

Right now I have a Loader class, which will require() files. But everytime I'm within another class, I have to re-intiate this class ($loader = new Loader; ). This doesn't seem like good practice to me. I'd rather have the ability to use the already initiated class, from wherever I'd like. So for example the core initiates the Loader class, and class1, class2, class3, etc, that are loaded from the core, can use the same Loader.

Please note that there's more to it than what I've written down here, so please don't try to work around the requiring issue 😉 it's about the structure. How to reuse certain classes, or being able to prevent the re-initialisation of a class.

Hope it's a bit clear. Thanks!

laserlight

It sounds like Loader should be a singleton, or perhaps simply a function. It depends on what exactly does it do.

Desdinova

Some things could be placed in functions. But I'd rather have them in classes, for structuring purposes. Say validation functions to validate emailaddresses, urls, addressdata, etc. I'd like to have a class Validation for that, instead of a file with just these functions. What do you think?

And about the singleton, I've never heard of it before but looked into it. It seems PHP cant handle this below PHP5.. 🙁

laserlight

But I'd rather have them in classes, for structuring purposes. Say validation functions to validate emailaddresses, urls, addressdata, etc. I'd like to have a class Validation for that, instead of a file with just these functions. What do you think?

I think that it is better to use classes to model objects, and then use proper namespace functionality for functions that are better off as free functions. However, PHP 4 and 5 do not have namespaces, so if you want to resort to classes to provide namespace functionality, go ahead, but those functions should be static member functions since they do not make sense as normal member functions. Consequently, you would not need any objects either, since you only invoke static member functions.

And about the singleton, I've never heard of it before but looked into it. It seems PHP cant handle this below PHP5

PHP 5 provides for private and protected member access, so it can enforce a singleton. However, you can disallow direct instantiation of the singleton by convention in PHP 4.

Desdinova

you knock me off my chair with all those terms 🙂
I need research.
I'll be back.

laserlight

you knock me off my chair with all those terms

Heheh. For a better explanation:

namespace: some way to group names
static member function: a function that belongs to a class, but does not need to be called from an object
singleton: an object that is the only one of its type
instantiation: the creation/construction of an object

Desdinova

Thanks, that made some more sense.

I'm still going to look into these static, public and private things. Ive only been working with php4 but a server with 5 is being set up, so sooner or later I'll have to know anyway.

ok. static member function.

class Classname {
 function do(){ return "a"; }
}

you wouldn't want me to do:

$obj = new Classname;
$var = $obj->do();

but

$var = Classname::do(); #which is a PHP5 function

the idea behind the class would be only the grouping of functions, and the class itself would serve no other purpose.

if this is correct, this part seems clear.

The singleton;
PHP5 seems clear, and the idea behind the singleton seems clear as well. Disallowing direct instantiaton by convention. What do you mean with 'by convention'? Googling only gives me meetings 😉

And thanks for helping me out here, I appreciate it.

Desdinova

I just found out that not using $this-> within a class, allows it to be called in a way I thought was limited to PHP5 (classname::function())

This enables me to process the class the way I'd like 🙂 (namespacing)

laserlight

Disallowing direct instantiaton by convention. What do you mean with 'by convention'?

You write a big fat comment that says: YOU ARE NOT ALLOWED TO CALL THE CONSTRUCTOR OF THIS CLASS ON PAIN OF DEATH. Then the user of the singleton class will use a static member function (typically named instance() or getInstance()) to get the object of the class. This static member function will check if the object already exists. If it does, it returns it by reference, if not, it constructs a new object, stores it as a static member variable, and returns it by reference.

But you know something. I just realised that I am wrong. It is very difficult to properly use singletons in PHP4. This is because:

PHP4 objects really are objects, not pointer-like references. However, PHP does not allow you to customise the copying behaviour of objects via their class definition. This means that in order to avoid copying, you have to pass and return the object by reference. Fail to do so, and the singleton is no longer a singleton.
From what I read of the PHP manual (yes, I have not used PHP4 in some time), PHP4 does not support the static keyword in a class context. However, a singleton class must store its singleton object. The only workaround I can think of is for the singleton object to store a reference to itself, but I am not sure if that is allowed, and if it is, it might lead to disaster because of problem #1.

Desdinova

What is your opinion on this:

class Bar {

function Bar(){
die("don't instantiate Bar");
}

function checkit(){
echo "works";
}

}

Might be better than a comment I think?

laserlight

Might be better than a comment I think?

Then how are you going to construct an object?

Desdinova

I won't, because I didn't need the object itself, but only use the functions of it?

I thought that's what you ment when you said I didn't need the object.

think that it is better to use classes to model objects, and then use proper namespace functionality for functions that are better off as free functions. However, PHP 4 and 5 do not have namespaces, so if you want to resort to classes to provide namespace functionality, go ahead, but those functions should be static member functions since they do not make sense as normal member functions. Consequently, you would not need any objects either, since you only invoke static member functions.

the loader would contain a function load() for example, and it would be called by using Loader::load();, without instantiating the class?

laserlight

I won't, because I didn't need the object itself, but only use the functions of it?

Oh yeah, I forgot that you wanted to use the class as a namespace. So yes, then that is okay.

Desdinova

great. I'm catching on. Thanks a lot, I can do something with this.