OO Programming

Anon

Well I have read so many tutorials, and I understand how classes/objects work, but I am still trying to understand how to put them in good use. Its said that OO programming makes your code much more elegant and portable, but im still confused on its usage.

Classes are made up of variables and functions, that are basically bundled into a ball which is the class.

Now im trying to figure out the difference of say having 4 functions in a class versus having those 4 functions in say some include without them being in a class?

Ive read the tutorials about OO/classes here at phpbuilder and also at zend.org

Any other good ones that might help me out? lets here some feedback because I know im not alone, regarding this subject.

Regards,
Derek C.

Anon

Derek,
Let me be the first to say I understand your agony - I remember my first stumblings into Object Oriented programming back in my Pascal days, Borland TP7 had just been released and the previous version had been the first to have object support.

It seems to me like you understand the concepts, but have questions about 'why'... I may be wrong in that interpretation of your message, but that is what I'll elaborate upon.

Classes (objects) make things more self-contained. Any good programmer already contains related functions within seperate library files - which is why you can #include things in C, require("") them in PHP, and use() them in other languages. Object orientation just takes this one step further.

Let's use a building as an example object, and functions that can be performed in that building as it's methods.

Our building has doors, as some buildings are might to do. I personally think that we should be able to open and close them, so say we have a function called open_door() and close_door() within the class. As they are inside the class, they are methods of the object.

Now, your question, as I read it again, pertains to why do it this way, instead of having the functions globally accessable. That becomes fairly simple, now - why should we make everything be able to call open_door(), when the only object that is going to use it is building? say you had an object called bicycle - there would be no use for it to open_door(), because it has no doors!
OOP is all about encapsulation.

Encapsulation makes your code cleaner, tidier, more legible to those who have eyes for such things, and basically easier to deal with.

I don't think I've ever read a good tutorial that explains the 'whys' of OOP - so I can't point you at any. But I hope my little random escapade helped explain a little.

Anon

Thanks for the reply, and yes this did help me for understanding a bit more on what classes are used for. Thanks again.

Now im starting to think that classes should or are mainly used when you basically want to use code over and over again, but not for one site, for a different project?

As you saying with your example, you have a class called building. Now in this class you have functions as open_door() close_door(). Now these wouldnt work for say a car. So it makes your code portable. But i still dont understand how that exact code for building will work for the car? because the open_door, close_door will probably always different.

Thats a bit confusing with that example but my point is. classes make your code portable no? If so, when are you ever going to use the SAME code for different projects or sites? im very confused! And if you were to use the same code, why wouldnt you just use the same functions.

Now after thinking this over im a bit more confused on OO 🙂 Let me think about this somemore. If possible, is there a good real world example you could show me here?

Derek

Anon

I might have an example here, tell me if this makes any sense!

1 thing that im always doing in a project is say updaing, inserting data to MySQL.

For example i would have a class named user

I would have a few functions in there like, insert(), update(), delete()

Now this would help me NOT repeat my code over and over on different pages, instead i would just be calling these functions for that class.

But yet again i come back to my point on why put these functions in a class? Why can't they just be global functions? Ok maybe they are only used for users but either way users are only going to use them.

Hmmmm.. the confusion continues.

Derek

Anon

Disclaimer: I'm in no way a good OO programmer, but I have hacked around with it for awhile, at least in one regard.

You are almost there with this one. I created an object that I use to connect to my MySQL database and run the queries. So now instead of having a lot of mysql_connect(), mysql_query() mysql_fetch_row() type calls in my code I have just a simple:

$db = new DBConnection();
$db->doQuery("SELECT SOMETHING", $array);

And now I have a nicely formatted array of the data that I selected. My array happens to be 1-based and multi diminsional so I can get at the data using $array[1]["COL_NAME"] and that will give me the value of COL_NAME that is in positon 1 of the result set.

I hope this helps.

Anon

Taking another angle on this whole OOP concept and why.

How about abstraction?

One big concept you should design into any data driven site is database abstraction. This will allow you to change databases (ie. from Access to MySQL, Oracle, etc. ) without any changes to your underlying site code.

As you probably know, accessing a MySQL database is different than say, an Oracle database, but the process should be the same.

You make a connection to the database.
You query the database.
You read the result set for display.

Abstraction will keep the class definition the same, but what goes on inside may be quite different. Who cares how it does it, I just need it to do it.

Example
class math_class{
var $number1;
var $number2;
var $result
function multiply_numbers();
$this->result=$this->number1*$this->number2;
}
return $this->result;
}

Example 2 (Note Same Class Name)
class math_class{
var $number1;
var $number2;
var $result;
function multiply_numbers(){
for ($i=0; $i<$this->number2; $i++){
$this->$result=$this->result+$this->number1;
}
return $this->result;
}
}

As you can see the inner workings of the multiply_numbers is quite different, but the outcome is always the same. (Unless I screwed up a technical detail).

Hope this helps. The benefeits of OOP in a web environment are just starting to reveal themselves to me.

Disclaimer: I am not an expert programmer and an even worse writer. Hope this wasn't to long of a response.

Good Luck!

Anon

No it was another good point on why and how to use Classes/Objects Chris. Thank You.

But im still trying to understand why all these functions are put into a class instead of them being global, like just straight up function inside of nothing. This is the part im most confused about at this point. I understand how it works, and understand how to put a class together, but I'm still not catching on.

Basically my question is that. Why creating classes with functions inside then having no class and just a file full of global functions?

Derek

Anon

Maybe I wasn't clear on why I had my database connections in a class. The mysql and other database functions in PHP all require that you send them a database link (they do use the most recent open link if you forget it). Because of this it isn't easy to open a connection to 2 different databases and move data around. You'd have to open one do your queries, open the other do queryies, and then open up the original again.

By using a class I have the database connection held inside the object that is created. This lets me create a class global variable that can be used in all of the functions inside my class, without interfearing with any of the variables or functions outside my class.

Anon

This is getting deep! I just read the thread and am beginning to understand more and more of it myself. To be honest with you for now, I am going to finish the project that I'm working on now using a function library or libraries, but seriously consider this into the future.

Now is it safe to say that these objects are like agents or entities that carry out particular duties for you? The particulars of those duties are not know to the rest of the program, only the outcome? If the above is correct, how is information passed to them?

Thanx,
Terrence

Anon

Ok I understand that a bit more... bit complicated but I think I understand what you are saying. Hopefully I can see the light with OO Programming, but for the time being it is still a bit fuzzy. Thanks again.

Derek

Anon

Hey Derek,

I thought you might want to check out this link on the topic being discussed here. I'm actually reading right now, and thought of this thread. Here is the link....

http://www.devshed.com/Server_Side/PHP/BackToClass/

It's rather good so far. Hope it helps.

Later on,
Terrence

Anon

Also, one of the authors on this site had the same experience you are having, I believe, derek - check his column out.

http://www.phpbuilder.com/columns/rod19990601.php3

Anon

Well it is about time... my entire view on OO Programming has been a total turn around. I guess its hard to explain to someone how OO Programming can help and make your code much more portable.

I was working on a mailing list project where it finally hit me! Basically what made me figure how and why to use it was simply this:

I had a bunch of functions, each did a little piece work. But in some functions i needed to perform other functions that I have already created.

This is where i totally seen the light.
OO Programming is definatly the way to go.

If anyone ever reads this thread of messages and is a bit confused about OO Programming and why to use it, feel free to give me a shout, ill try to show you the light 🙂