PHP OOP real-world guidance needed

bernk

Dear programmers of the information super space highway web,

I need your guidance.

I've been trying now for a long time to wrap my head around OOP. I see its advantages. I've read many, many tutorials and watched an equal amount of videos on the subject. I get the animal/cat/dog examples, I get the car/drive examples. What I'm struggling with is how to apply these concepts in a real-world application. So, I've set out to build one using OOP.

I am not asking for help with syntax or writing specific code — I can find that myself in documentation and by searching forums etc.. What I really need is some guidance, and a push in the right direction every now and then. Are there any seasoned programmers willing to mentor me?

As my learning project I would like to build a simple classifieds "web app". Something similar to Craigslist but way watered down in terms of scope. I would like to use PHP5 and MySQL, because I am familiar with them.

Let's say there are only these 2 use cases:

Posting something for sale
Browsing/searching for something to buy

What "things" should be objects? I can imagine that each item could be an object, but at what point? And why?

So for example, the user fills out the "post item for sale" form, should that form get turned into an object which gets passed to another object which inserts the values into a database?

What about when another user is browsing and requests to see all items of category C? Does it make sense that whenever the app has to connect to its database it creates a database object and then gets a bunch of item objects and displays them on the page? …writing this out certainly makes me realize how clueless I still am about OOP. Please help me fix that.

If in your opinion this is not a good project to start wading into OOP with, please feel free to suggest another idea!

Thank you.

Lord_Yggdrasill

Well in a perfect script everything is an object, the difficulty is how you can envision everything as an object.

You can start off by creating a core class that loads a list of useful system objects. Id recommend you to look into the idea of MVC and learn how to use it. I am not that good at MVC yet, so guess I have to get better too.

Whenever you use arrays, think of ArrayObject and make an array into object. There is even a string class available, so you can make your strings into objects too. This is not recommended though, as PHP has yet to introduce a StringObject extension similar to ArrayObject. User defined classes tend to be less efficient than built-in classes.

It will also be necessary to create a document class with child classes such as table and form extending it. Do not use echo in your main script, and instead use an output() method for your core class to echo strings.

Of course you cannot create a perfect script since not everything in PHP can be made into objects, Hope this advice helps.

Derokorian

Both of you need to read PHP - Objects, Patterns, and Practice by Matt Zandstra Best book I've ever read regarding objects, specifically objects in PHP.

Lord_Yggdrasill

Actually I just ordered the book 2 days ago, it should arrive soon and guess I will learn a lot from it. I know its impossible for everything to be an object in PHP since its not a pure OOP language like Ruby, but I will try to see how much closer I can reach this goal.

Lord_Yggdrasill

bradgrafelman;11004359 wrote:
... if and only if your opinion is that a "perfect script" would have such a requirement. 😉

Actually the fact that PHP is not fully object oriented means that its not a perfect programming language yet. XD

But well, PHP has been constantly improving and adding new features, I wont be surprised that someday it becomes possible to create a perfect script in which everything is an object. It may take a while though, but worth waiting.

Oh btw I do love PHP's syntax though, but Id say this is a matter of preference.

Bonesnap

Many people have differing opinions on how to organize their projects and when it's the best time to create classes.

Personally, I only create classes for "things" and not concepts. For example, in a forum I'd create a class for thread, user, post, etc. but probably not for something like database connection. I know a lot of people do it, I just personally don't. The great thing about programming is there's always more than one way of doing things.

I also tend to not create a lot of member functions and instead use classes and objects more for organizational purposes.

In the case with something similar to Craigslist, you may have a class for an ad, that contains all the properties associated with an ad. You'd probably also have a class for a user as well.

Derokorian;11004356 wrote:
Both of you need to read PHP - Objects, Patterns, and Practice by Matt Zandstra Best book I've ever read regarding objects, specifically objects in PHP.

Lord Yggdrasill;11004357 wrote:
Actually I just ordered the book 2 days ago, it should arrive soon and guess I will learn a lot from it. I know its impossible for everything to be an object in PHP since its not a pure OOP language like Ruby, but I will try to see how much closer I can reach this goal.

The book is available free on Google Books. Link

Derokorian

Yeah I purchased it before it was available for free, so I have a hard copy heh.

Also, if you're so stuck on something has to be 100% OO to be perfect, then why use PHP at all? Why not use .NET or Ruby or Java and get out of our partially procedural world! ;-)

Lord_Yggdrasill

Well because PHP's syntax makes more sense to me? And more importantly, I am a web developer and I work on Web applications, which means that PHP is the best choice. Not mentioning that my partner coders are PHP programmers. Anyway sorry I did not mean to be offensive. Not trying to downplay PHP, its a great programming language.

And regarding the OP's question. Id say using either MySQLi or PDO, the former is pretty much an object-oriented version of PHP's MySQL functionality, while the latter is more standardized and supports more than just MySQL. PDO statement's fetch() method is more powerful and you can fetch database info into object properties using PDO::FETCH_INTO. Not sure if this is what you want though, but these database object extensions will work out nicely.

laserlight

Lord Yggdrasill wrote:
Of course you cannot create a perfect script since not everything in PHP can be made into objects

Lord Yggdrasill wrote:
I know its impossible for everything to be an object in PHP since its not a pure OOP language like Ruby, but I will try to see how much closer I can reach this goal.

Lord Yggdrasill wrote:
Actually the fact that PHP is not fully object oriented means that its not a perfect programming language yet. (...) I wont be surprised that someday it becomes possible to create a perfect script in which everything is an object.

I'm going to be blunt now: I think you're just being an OOP fanboy/fangirl. OOP is a tool, a programming paradigm to model and solve programming problems, not an end in itself. Having everything as objects does not make for good object oriented design in itself. Depending on the situation, other programming paradigms, or a combination thereof, may be more suited to solve the given problem.

vivek151189

yes i agree with laserlight

bernk

Thank you all for your responses. Bonesnap came closest to what I was looking for. As an example, at what point would an ad become an object? How does an OO back-end relate to the front-end? I guess that's more what I'm having trouble understanding.

Let's switch to a very simple message board example where a user logs in and posts/edits/deletes messages. That's all. So let's say I have index.php which shows a complete list of all the messages in the DB. Normally for something this simple I would have index.php contain all of the HTML and a loop somewhere in the body which would iterate through the messages table to echo each message out into html. Would you on each iteration of the loop take the data from the messages table and store it in an object? What about when the user wants to login to post more messages? How should/could the user be represented by an object?

Lord Yggdrasill, no programming language is perfect. Like laserlight said, languages are essentially tools. The task at hand dictates which tool or approach is right for the job. I'm guessing by "perfect" you might have meant "finished" … which nothing really is either ; )

Bonesnap

bernk;11004499 wrote:
As an example, at what point would an ad become an object? How does an OO back-end relate to the front-end? I guess that's more what I'm having trouble understanding.

Let's switch to a very simple message board example where a user logs in and posts/edits/deletes messages. That's all. So let's say I have index.php which shows a complete list of all the messages in the DB. Normally for something this simple I would have index.php contain all of the HTML and a loop somewhere in the body which would iterate through the messages table to echo each message out into html. Would you on each iteration of the loop take the data from the messages table and store it in an object? What about when the user wants to login to post more messages? How should/could the user be represented by an object?

On your page where you're listing ads, you would query the database for the necessary information. When you retrieve it, you'd create an Ad object with the information from the database then use that object to display information on the page.

As an example, here's the source code to my forum where a user can view a single post.

Pastebin link

And here's the code for the get_post() function, which returns a Post object:

/**
 * Gets a Post object from a post ID.
 *
 * @since version 2.0
 * @param int $pid The post's ID.
 * @return Post|false Returns a Post object or false on failure.
 */
function get_post($pid)
{
	$query = "SELECT post_id, posts.user_id, user_name, posts.thread_id, thread_title, 
					 thread_status, section_name, sections.section_id, post_date, 
					 post_message, post_status, post_ip, post_edit_date, post_edit_uid
			FROM posts
			NATURAL JOIN users
			NATURAL JOIN threads
			NATURAL JOIN sections
			WHERE post_id = ".$pid;

$result = mysql_query($query);
if($result)
{
	$row = mysql_fetch_assoc($result);
	$post = new Post();
	$post->id = $row['post_id'];
	$post->user_id = $row['user_id'];
	$post->user_name = $row['user_name'];
	$post->thread_id = $row['thread_id'];
	$post->thread_title = $row['thread_title'];
	$post->thread_status = $row['thread_status'];
	$post->date = $row['post_date'];
	$post->message = $row['post_message'];
	$post->status = $row['post_status'];
	$post->ip = $row['post_ip'];
	$post->edit_date = $row['post_edit_date'];
	$post->edit_uid = $row['post_edit_uid'];
	$post->section_id = $row['section_id'];
	$post->section_name = $row['section_name'];
	return $post;
}
return false;
}

As you can see in the view post source, I am creating a Post object based on information I have retrieved from the database, and then using that object to display information about the post an the page. This could easily be done other ways but I prefer this kind of approach.

bernk

Thanks for taking the time to share your code. Much appreciated!

Lord_Yggdrasill

Bonesnap;11004504 wrote:
On your page where you're listing ads, you would query the database for the necessary information. When you retrieve it, you'd create an Ad object with the information from the database then use that object to display information on the page.

As an example, here's the source code to my forum where a user can view a single post.

Pastebin link

And here's the code for the get_post() function, which returns a Post object:
/**
 * Gets a Post object from a post ID.
 *
 * @since version 2.0
 * @param int $pid The post's ID.
 * @return Post|false Returns a Post object or false on failure.
 */
function get_post($pid)
{
	$query = "SELECT post_id, posts.user_id, user_name, posts.thread_id, thread_title, 
					 thread_status, section_name, sections.section_id, post_date, 
					 post_message, post_status, post_ip, post_edit_date, post_edit_uid
			FROM posts
			NATURAL JOIN users
			NATURAL JOIN threads
			NATURAL JOIN sections
			WHERE post_id = ".$pid;

$result = mysql_query($query);
if($result)
{
	$row = mysql_fetch_assoc($result);
	$post = new Post();
	$post->id = $row['post_id'];
	$post->user_id = $row['user_id'];
	$post->user_name = $row['user_name'];
	$post->thread_id = $row['thread_id'];
	$post->thread_title = $row['thread_title'];
	$post->thread_status = $row['thread_status'];
	$post->date = $row['post_date'];
	$post->message = $row['post_message'];
	$post->status = $row['post_status'];
	$post->ip = $row['post_ip'];
	$post->edit_date = $row['post_edit_date'];
	$post->edit_uid = $row['post_edit_uid'];
	$post->section_id = $row['section_id'];
	$post->section_name = $row['section_name'];
	return $post;
}
return false;
}
As you can see in the view post source, I am creating a Post object based on information I have retrieved from the database, and then using that object to display information about the post an the page. This could easily be done other ways but I prefer this kind of approach.

Umm interesting, I was wondering what this Post object does. Is it just a stdclass, or does it have some methods?

Bonesnap

bernk;11004505 wrote:
Thanks for taking the time to share your code. Much appreciated!

You're welcome!

Lord Yggdrasill;11004506 wrote:
Umm interesting, I was wondering what this Post object does. Is it just a stdclass, or does it have some methods?

No it's an actual defined class, and no, it does not have any methods. It's basically a way for me to organize information, mostly for displaying it.

Weedpacket

Bonesnap wrote:
No it's an actual defined class, and no, it does not have any methods. It's basically a way for me to organize information, mostly for displaying it.

Have you considered using mysql(i)_fetch_object? You can specify a class name and have it create and populate an instance of that class.

Bonesnap

Weedpacket;11004532 wrote:
Have you considered using mysql(i)_fetch_object? You can specify a class name and have it create and populate an instance of that class.

Hmmm, never really thought about that. It would come in handy for several of my classes, that's for sure. I'll have to look over my other classes to see where it can be implemented. Thanks for the tip!