I'm trying to design a solid server side architecture and came up with this :
http://www.monsterup.com/image.php?url=upload/1235488072.jpg
The client side only talks to a single server file called process.php, where user rights are checked; and where the action is being dispatched. The business classes then handle the business logic and perform data validation. They all have contain a DataAccessObject class that performs the db operations.
Could you point the different weaknesses such an architecture may have? As far as security, flexibility, extensiveness, ...?
Your architecture isn't perfect. It never will be perfect. Ever. Being perfect is impossible. This is the nature of application development, programming, and the world in general. A requirement will come in to add a feature, or change your business logic and you'll return to this architecture and say "What in the world was I thinking this is terrible." (Hopefully... otherwise you probably haven't been learning anything new!)
Take an inventory of your goals, should it be:
this architecture perfect
or instead:
this architecture functions where I need it to and allows me to get stuff done
One way that you could improve this is to add a view layer, using a template engine such as Smarty, or even roll-your-own. The action classes would prepare the data, assign it to the template, then display the template itself.
That would help you to separate your business logic from your HTML, making it easier to maintain.
This is a common way to design an application.
Another thing you could do is have another class handle the action delegation. It really depends on the complexity of your application, though.
The book PHP Objects, Patterns and Practice can give you a real leg-up on application architecture.
I see a couple of things.
First, I agree with others that you should add a view layer of some kind, though I am not sure about Smarty (I use it frequently and I am really having doubts these days, but I digress). The point is you need to separate your HTML somewhere in a template so it's easy to change. That point does not waver if you use a lot of AJAX. AJAX still requires you (usually) to put divs around the page, etc. So your layout should be separated from processing code.
The second thing I would throw out there is the complexity of your data model matters. If this is a straightforward CRUD application over an existing, or fairly flat, db model, you are probably fine with these db access classes. But, the minute your model gets to be more complex, with hierarchies or polymorphic in any way, this will break down. You'll need a more robust ORM of some kind.
Your "controller/dispatcher" methodology seems sound. The switch statements avoids the need for any kind of URL -> code mappings, which are a pain to manage and require caching to scale.
That's my $0.02
From a security perspective your class and action are coming in from your post variables and this can be dangerous because you should never trust anything coming from the user. Assumingly your class/action will look something like this:
class1
{
action1.1
action1.2
...
action1.N
}
class2
{
action2.1
action2.2
...
action2.N
}
As an attacker my first place to look would be getting into a state where an action doesn't match to it's appropriate class. I would try to submit class1 with action2.1 instead of action1.1.
With that said, my assumption is that you've already got some form of validation and so this wouldn't happen. Which leads me to my original post: If your architecture works for you, then it works for you. Take a look at the things which you're asking about: security, flexibility, extensibility and evaluate them yourself. Find your own flaws. If you don't know how to evaluate for security/flexibility/other read up on the subject, practice it and apply it.
You'll become a better developer by making mistakes and then learning from them (except missile guidance software, you only get one try there.)
Since others have suggested various changes like adding a view layer, etc. let me concentrate on the various criteria for a good architecture:
Extensibility: Usually, the more abstract and loosely coupled the architecture is, the more extensible it is. This is exactly why others have recommended you use a view layer which would abstract out the presentation layer templates for each class:action pair into its own file.
Maintainability: This goes hand-in-hand with extensibility. Generally, the more extensible the architecture is, the more maintainable it is (take that with a grain of salt because it is not always the case). Consider adding a model layer below your model logic layer. This would help you swap out your data access logic from the model business logic.
Security: The downside to the architecture you have posed is that you really need to invest in security testing. Since all your redirecting/routing code is in process.php, that file has a lot of responsibility and any changes to it may result in a potential security loophole. This isn't necessarily wrong, you just need to be aware of the risks.
Scalability: Your architecture is balanced and seems very scalable. Since you have it broken down by class:actions, you can add caching at any layer to improve performance. Adding an addition data access model layer will also help you cache at the layer closest to the database.
Finally, experiment with each architecture and don't be afraid to make mistakes. It already seems like you have a good understanding of MVC. The only way to get better at architecting is to implement and test it in the 'real world'.
Related
I've been learning OOP programming for about a year and a half now and have developed a fairly standard framework to which I generally abide by. I'd love some feedback or input on how I might improve some functionality or if there are some things I'm overlooking.
VIEW MODE
1) Essentially everything starts at the Index.php page. The first thing I do is require my "packages.php" file that is basically a config file that imports all of the classes and function lists I'll be using.
2) I have no direct communication between my index.php file and my classes, what I've done is "pretty them up" with my viewfunctions.php file which is essentially just a conduit to the classes so that in my html I can write <?php get_title('page'); ?> instead of <?php echo $pageClass->get_title('page'); ?> Plus, I can run a couple small booleans and what not in the view function script that can better tailor the output of the class.
3) Any information brought in via the database is started from it's corresponding class that has direct communication with the database class, the only class that is allowed direct to communicate with the database (allowed in the sense that I run all of my queries with custom class code).
INPUT MODE
1) Any user input is sent to my userFunctions.php.
2) My security class is then instantiated where I send whatever user input that has been posted for verification and validation.
3) If the input passes my security check, I then pass it to my DB class for input into my Database.
php general model http://img139.imageshack.us/img139/3319/phpmodel.gif
FEEDBACK
I'm wondering if there are any glaringly obvious pitfalls to the general structure, or ways I can improve this.
Thank you in advance for your input. I know there is real no "right" answer for this, but I imagine a couple up votes would be in order for some strong advice regarding building frameworks.
-J
One thing I would recommend you do is to go ahead and separate your functions into classes. I understand the points you made about avoiding instantiations but consider this: any framework will, by necessity, begin to accumulate a large number of functions.
Instead of doing
<?php get_title('page'); ?>
you would be better served to create a Page class with all of its functions inside of said class which you call statically. Then, your code becomes
<?php Page::GetTitle('page'); ?>
a much more descriptive naming convention and will become critical later on when trying to avoid naming collisions (you only have to avoid name collisions on say, 50 classes, rather than two thousand functions).
I would study up on the Model-View-Controller design methodology (as ircmaxell hinted at in his post). A lot of very powerful and very well-written frameworks apply this principle, and not just PHP frameworks either. My suggestion - study Yii for how your application should be controlled - very slick and the creator makes excellent use of static variables to control class instantiation.
Good luck with your framework!
Well, the only issue that I can see (without seeing code), is that SQL will be everywhere. What I'd suggest is creating a "model" layer in front of the DB connection class. That way, all your sql is in one spot (break it off into multiple models, etc). It makes maintenance MUCH easier (if you want to add a column to a table, optimize a query, etc)...
Otherwise, it looks like a good start!
Nice presentation. I would definitely look under the hood at other popular frameworks for some insight.
At first glance, I would suggest to see if you can find a way to only load the classes you need per request. Loading them all for every request may become unfeasible if the class library grows large.
Are you using autoloaders? It seems that you will be using a lot of requires... maybe I am just misinterpreting. I think it is great that you are writing your own framework. I don't see it as "reinventing the wheel" either as you are writing it to accomplish the tasks you want to accomplish and can control the overall weight of your project as well as, since you are by most standards still moderately new to OOP, learning a ton I am sure from the experience. Creating your own frameworks, trying to improve other peoples code and learning how others do things and why is an amazing learning experience and in my opinion will drastically improve your programming skills and understanding.
I do not have much experience using frameworks or anything so that leaves me with little experience using Models (MVC). I have no interest whatsoever in using a framework at the moment. I am working on a website and I am trying to model some objects but I'm not sure exactly how I should be designing the class.
For instance, right now I have a class with a few public members which can be accessed directly. I have started prototyping some functions (select, delete, update) but I am not sure
If these functions should be static
If these functions should accept parameters or use the class members instead
If these functions should even exist how they do currently
If the entire concept I'm going for is the right thing to do
I can't seem to find any sort of hints on the interwebs as to how to create a model class.
If you're using a factory class then all verbs are usually instance methods and the factory is instantiated with some sort of DB session.
If the verbs are member's of the entity's class select is usually a static method while update is usually an instance method and delete is usually defined both ways (IE: delete(recordID) and entity.delete())
The entire concept is the right thing to do but you're going to do it wrong. Period. Making a scalable model like this takes a lot more time and effort than people have at their disposal. I know you have no interest in using a framework but you should.
My inference from your question is that this is a low profile project, and you have enough flexibility from your boss/client/teacher that you can build it however you want. That in mind, here is what I would think about when working on this.
If MVC is a new concept to you, then Test-Driven Development is almost certainly and alien one as well. However, I first cracked into a real understanding of OOP while doing it, so I suggest you give it a try. Writing some simple unit tests first against your model classes will take you through the exercise of figuring out how those model classes are going to be used. You'll be working with the external API of each of those objects (or groups of objects if you're not a TDD purist), and that will help guide the design of the internals. Check out PHPUnit for getting started, as the documentation has some great examples as well.
I think the TDD approach will lead you to the following conclusions:
Probably not. Static data/methods are usually only useful when you absolutely need one copy of something. I find in web apps that aside from maybe a resource connection like the DB this is rarely the case.
This depends on what the function does. Keep in mind that using local variables implies side-effects, or changes in the state of the object. If the data you need to operate on should not change the state of the entire object, use a parameter and return a value. It's also easier to test these kinds of methods.
Again, writing tests for these functions that illustrate how you'll use them in the application will lead you to a conclusion one way or another about whether you need them or whether they are designed correctly. Don't be afraid to change them.
Absolutely. How else are you going to become comfortable with MVC if you don't roll your own implementation at least once? In fact, it's probably better to grasp the concepts with real experience before you move to a more professional framework. That way, you'll understand why the concepts and conventions of the framework are the way they are.
Oh, and the lack of clarity that you're finding on what a model class is, is probably due to the fact that it's the part of your application that is most customized. This is your data model and domain logic, so a lot of it is case-specific. The best resource, though, IMHO is Martin Fowler, whose excellent book Patterns of Enterprise Application Architecture goes into a lot of detail on how and why to design a particular set of "model" classes with one pattern or another. Here is the online pattern library--obviously the book is more detailed.
Hope that helps somewhat.
When using PHP, I think designing object oriented model adds extra work with little benefits - even when looking on large frameworks, it's common to just use assoc-arrays that you can get from resultsets (see f.ex. the multiparadigm approach of Zend MVC).
While Object-Relational mapping is much more established among strongly typed languages like Java, there are already tools for PHP as well (f.ex. Doctrine). You may check it out if having OO-oriented model is what you want, but be aware that OR-mapping has severe issues of it's own and might be of little use in PHP (haven't tried it myself in a dynamic language yet).
For most newly started project, picking a good framework is usually a way to go - it can save you time and promote best practices (of course after some learning time that's different for every tool out there). When using some framework, you should always try to find out the framework's / community approach to solving specific problems (like model design & data access) before experimenting on your own.
The "correct" way to abstract away data access using object-oriented concepts is a hot-button topic for a lot of people. Put another way, there are several ways to do it and there is no "one right" way.
Rolling your own works best if you are seriously upgrading an existing application. This is because you have a heap of code that is already database dependant and you have some bounds for the necessary refactoring. It also teaches you about abstracting code because a lot of refactoring involves removing (or reducing) code duplication. Once you've done this to completion, you will have a much better idea of how a data model layer should work. Or at least, should work for the way you program. And you will know what not to do next time you build one. :-)
If you're starting a new codebase and haven't worked with a framework or object layer but know you need to build one, then the best advice I can give is to be willing to build one later, and refactor the code to suit when that does happen. Yes, it will likely mean your application will get 90% rewritten a few times.
Writing an object abstraction layer is difficult and you will end up with dense code that is fairly defensive about things, and doesn't take chances. But once you've got it working, you will also know how to build robust code, because it will probably be debugged fairly thoroughly.
No because, static methods are hard to test
It depends of the parameter, life cycle, etc. Impossible to answer without seeing some code.
?
No
OOP requires at least 10 years of experience to have a better view on what is wrong/right/better/worse.
So, if you are not a OOP expert, instead of losing too much time reinventing the wheel, I would suggest:
Use a well-known framework for the technical part
Create your classes/framework for the business/functional part.
(1) Will help you be ready in no time for the classic technical part (Session, database interaction, etc.). Will avoid you to make errors others already did.
(2) This is your core business, it should be "your DNA".
Also, using a well-known/good technical framework will make you read quality code and help you progress. (Be carefull some frameworks are really of poor quality)
When you will have enough experience, you will be able to skip the technical framework part and build/customize your own... because technical framework are usually evil (They serve too many purposes). :)
I'm going to write a framework for my web projects in PHP.
Please don't tell me about considering to use some existing framework (Cake, CodeIgniter, Symfony, etc.) - I have already had a look at them and decided to write one for myself.
The framework itself will mainly consist of a module system, a database handler and a template parser. (Many other things too, of course)
With module system I mean that every module has exactly one PHP file and one or more templates associated with it.
An example module would be modules/login.php that uses templates/login.tpl for its design.
These days everyone(?) is talking about the MVC (Model View Controller) concept and most of the existing frameworks use it, too.
So my questions are the following:
Is MVC really effective for a personal framework?
Would it be a bad idea to use a module system?
Did you ever write a framework for yourself? What are your experiences?
Is MVC really effective for a personal framework?
Yes, it can be. Although, it might be a little overkill (which, is not necessarily a bad thing if you are trying to learn)
Would it be a bad idea to use a module system?
This is never a bad idea.
Did you ever write a framework for yourself? What are your experiences?
I wrote a common security framework for my group's PHP applications when I was an intern. I learned alot, but the project as a whole might have benefited more from a pre-built solution.
Of course, I wouldn't have learned as much if I just installed a pre-built solution. So you always have to take that into account, especially for personal projects. Sometimes re-inventing the wheel is the only way you will learn something well.
Is MVC really effective for a personal framework?
What MVC means anymore, due to its vague interpretation, is business logic, presentation, and input handling. So, unless you aim to design an application that does not involve any three of those, MVC is, in its vague sense, very suitable.
Often it can be more formal than you desire, however, as it demands physical separation of ideas into different code files. Quick and dirty tasks or rapid prototyping might be more quickly setup if the formalities are avoided.
In the long term, what MVC asks for is beneficial to the sustainability of the application in ways of maintenance and modification or addition. You will not want to miss this. Not all frameworks encourage the right practices, though. I am not surprised that you find the various implementations you've tried insufficient. My personal favourite is Agavi. To me and others, in a world of PHP frameworks that do not feel right, Agavi emerges to do the right things. Agavi is worth the shot.
Would it be a bad idea to use a module system?
MVC asks you to separate components of business logic, presentation, and input handling, but it does not suggest how to layout the files. I presume this is the challenge you are addressing with a module system. To answer your question: modules serve identically to sub-directories. If the items are few, its probably more hassle to bother with subdirectories even if the files could logically be separated into them. When the number of items grow large, its now cumbersome to locate them all and sub-directories become a better option.
Frameworks will tack on functionality that allows you to deal with modules as their own configurable entity. The same functionality could just as well exist without modules, perhaps in a more cumbersome manor. Nonetheless, do not consider modules primarily as a system. Systems are so wonderfully vague that you can adapt them to whatever setup you find suitable.
Did you ever write a framework for yourself? What are your experiences?
Yes I have wrote several frameworks with various approaches to solving the issues of web applications. Every such framework I wrote became nothing but a vital learning curve. In each framework I made I discovered more and more the issues with building software. After failing to create anything interesting, I still gained because when asked to make a program I could fully do so with justice.
I recommend you continue if this is the sort of learning experience you want. Otherwise, give Agavi a shot. If that too fails, ensure that you have a clear and detailed specification of what your framework will do. The easiest way to barge into making software, work really hard, and accomplish nothing is to not decide before-hand what exactly your software will do. Every time I ran into making code the only thing in my mind was I will do it right. What happened was a different story: oh, well I need to make a routing system as that seems logical; hmm, okay, now I need a good templating system; alright, now time for the database abstraction; but gee, what a lot of thinking; I should look to the same system from software XXY for inspiration. Therein is the common cry that pleads to use existing software first.
The reason I thought I could do it right was not because all the nuts and bolts of the framework felt wrong. In fact, I knew nothing about how right or wrong they were because I never worked with them. What I did work with was the enamel, and it felt wonky. The quickest way to derive your own framework is really to steal the nuts and bolts from another and design your own enamel. That is what you see when building an application and frankly is the only part that matters. Everything else is a waste of your time in boilerplate. For learning how to build software, however, its not a waste of time.
If you have any other questions, please ask. I am happy to answer with my own experience.
I am also actually writing a php framework with a friend of mine. I absolutely can understand what you do.
I thing what you are doing is near mvc. You have the templates as views. And the modules as controller. So I think that is ok. The only thing you need is the model. That would be some kind of active records.
In my framework there are simular concepts, except we are writing our own active records engine at the moment. I think what you do isn't bad. But it's hard to say without seeing code.
I see only one problem you have to solve. A framework should be perfectly integrated. It is always a complicated to make your module look nice integrated without always have to think of module while you are coding application.
Is MVC really effective for a personal framework?
Would it be a bad idea to use a module system?
Yes it is. But MVC is such a loosy-goosy design pattern that you can draw the line between model, view, and controller anywhere you want. To me, the most important parts are the model and the view. I simply have pages, php modules, that generate html by filling in a template from a database. The pages are the view and the database is the model. Any common application-specific code can be factored out into "controllers". An example might be a common, sophisticated query that multiple pages must use to render data.
Other than that I have utilities for safe database access, simple templating, and other stuff.
Did you ever write a framework for yourself? What are your experiences?
Yes. I'm very glad I did. I can keep it simple. I know intimately how it works. I'm not dependent on anyone but myself. I can keep it simple yet useful.
Some pointers (0x912abe25...):
Every abstraction comes with a cost.
Don't get to fancy. You might regret not keeping it simple. Add just the right amount of abstraction. You may find you over-abstracted and something that should be simple became excessively complex. I know I've made this mistake. Remember You-aint-gonna-need-it.
Scope your variables well
Don't load your pages by doing
include_once('...page file ...');
where it's expected that page file will have a bunch of inline php to execute looking up different global variables. You lose all sense of scope. This can get nasty if you load your page file from inside a function:
function processCredentials()
{
if (credentialsFail)
{
include_once('loginpage.php');
}
}
Additionally, when it comes to scoping, treat anything plugged into templates as variables with scope. Be careful if you fill in templates from something outside the page file associated with that template (like a master index.php or something). When you do this it's not clear exactly what's filled in for you and what you are required to plug into the template.
Don't over-model your database with OO.
For simple access to the database, create useful abstractions. This could be something as simple as fetching a row into an object by a primary index.
For more complex queries, don't shy away from SQL. Use simple abstractions to guarantee sanitization and validation of your inputs. Don't get too crazy with abstracting away the database. KISS.
I would say that MVC makes more sense to me, since it feels better, but the only practical difference is that your login.php would contain both the model (data structure definitions) and the controller (code for page actions). You could add one file to the module, e.g. class.login.php and use __autoload() for that, which would essentially implement an MVC structure.
I have refactored a big PHP project to make it more MVC compliant.
I found especially usefull to create a DAO layer to centralize all database accesses. I created a daoFactory function, which creates the DAO and injects the database handle into it (also the logger, I used log4php, got injected).
For the DAO, i used a lot the functionalities of the database (mysql), like stored procedure and triggers. I completly agree with Doug T. about avoid over-abstraction, especially for database access : if you use the DB properly (prepared statements, etc.) you don't need any ORM and your code will be much faster. But of course you need to learn mysql (or postgress) and you become dependant on it (especially if you use a lot of stored procedure, like I tend to do).
I am currently refactoring a step further, using the Slim php framework and moving toward a restfull api : in this case there is no view anymore because everything is outputted as json. But I still use smarty because its caching works well and I know it.
Writing a framework could be a rewarding experience. The important thing to consider is that you do not write a framework for its own sake. The reason one writes a framework is to make development easy.
Since it is a personal framework you should think in terms of how it could help you develop with less hassle.
I do not think a template system is a good idea. Think of it - what is the major benefit of using a template system? The answer is that it helps teams with different skill sets jointly develop an application. In other words, some members of the team can work on the user interface and they do not need to be PHP coders. Now, a personal framework will most likely be used by a single person and the benefit of template system becomes irrelevant.
All in all, you should look at your own coding habits and methods and discover tasks that take most of your time on a typical project. Then you should ask yourself how you can automate those tasks to require less time and effort. By implementing those automation mechanisms you will have to stick to some sort of conventions (similar to an API). The sum of the helper mechanisms and the conventions will be your personal framework.
Good luck.
MVC doesn't work
you don't want to be constrained in the structure of your "modules"; also, keep templates close to the code (the templates directory is a bad idea)
no
re 1.: see Allen Holub's Holub on Patterns. briefly: MVC basically requires you to give up object oriented principles.
Tell Don't Ask is a catchy name for a mental trick that helps you keep the data and code that acts on it together. Views cause the Model to degrade into a heap of getters and setters, with few if any meaningful operations defined on them. Code that naturally belongs in the Model is then in practice spread among Controllers and Views(!), producing the unhealthy Distant Action and tight coupling.
Model objects should display themselves, possibly using some form of Dependency Injection:
interface Display
{
function display($t, array $args);
}
class SomePartOfModel
...
{
function output(Display $d)
{
$d->display('specific.tpl', array(
'foo' => $this->whatever,
...
));
}
}
OTOH, in practice I find most web applications call for a different architectural pattern, where the Model is replaced with Services. An active database, normalized schema and application specific views go a long way: you keep the data and code that acts on it together, and the declarative nature makes it much shorter than what you could do in PHP.
Ok, so SQL is a terribly verbose language. What prevents you from generating it from some concise DSL? Mind you, I don't necessarily suggest using an ORM. In fact, quite the opposite. Without Model, there's little use for an ORM anyway. You might want to use something to build queries, though those should be very simple, perhaps to the point of obviating such a tool...
First, keep the interface your database exposes to the application as comfortable for the application as possible. For example, hide complex queries behind views. Expose update-specific interfaces where required.
Most web applications are not only the owners of their respective underlying databases, they're their only consumers. Despite this fact, most web applications access their data through awkward interfaces: either a normalized schema, bare-bones, or a denormalized schema that turned out to make one operation easier at the price of severe discomfort elsewhere (various csv-style columns etc). That's a bit sad, and needlessly so.
re 2.: it's certainly good to have a unified structure. what you don't want to do is to lock yourself into a situation where a module cannot use more than one file.
templates should be kept close to code that uses them for the same reason that code that works together should be kept together. templates are a form of code, the V in MVC. you'll want fine-grained templates to allow (re)use. there's no reason the presentation layer shouldn't be as DRY as other parts of code.
I work in a web shop as a PHP programmer. Most of the time we use good coding practices but not much structure to the site as a whole.
I have now entered my phase of being bored with some of our practices and want to branch out and simplify and generate some things in a helpful way not just for me, but the hybrid-programmer web developers in the office.
One employee left us with a MVC site written in PHP, and I have had to maintain it a bit, and I get how it works but have my complaints, my main complaint is that it is tightly coupled with each piece dependent on another. I see the advantage of the seperation of concerns, but this would be confusing to anyone but me looking at the code.
So for example, if I need to add a new page to the site, I have to go add a view, and then add a model, then update the controller. The ad-hoc method of making a new page is way simpler than this and doesn't require a programmer.
My judgement was this was a much better method to build, rather then maintain, a website.
Still, it would be nice if I had some design patterns where I could reuse code effectively without it being dependent on a multiple places in the site.
So my question is, is there a design pattern for building and maintaining websites that is much more loosely-coupled? I'm not looking for slight variations on MVC, I need something quite different to look at, maybe some type of plugin approach.
EDIT:
Thanks for the answers so far! A different way of putting it is I want the code to be done better in my office. Do I A) Push for MVC or B) find/build an alternative not as confusing to the half-programmers. We already use classes for things like DB connectivity and Form helping. The point of this question was to explore B.
There's always a compromise between the code being confusing because it's highly deconstructionist, and the code being confusing because absolutely everything needed to do X is randomly scattered around a single file.
The problem with the latter is that exactly what is an "intuitive" way to split things up into monolithic modules differs between people. Highly decomposed and factored code is nearly always more difficult to wrap your head around, but once you do that, maintenance becomes both easy to do. I disagree that it would be confusing to anyone else but the author looking at it. Large-scope patterns like MVC are used because it becomes easier to spot them and work on projects structured around them over time.
Another advantage of using MVC is that you generally won't make the application more difficult to maintain for someone who comes after you if you don't stick to the layering. This is because now you have a predetermined place where to place any aspect of implementing a new feature.
As far as the tight coupling is considered, you can't really implement a feature without there being some connection between the layers. Loose coupling doesn't mean that the layers are ignorant of each other completely - it means that a layer should be unaware of how the other layers are implemented. E.g.: the controller layer doesn't care whether you're using a SQL database or just writing binary files to persist data at the data access layer, just that there is a data access layer that can get and store model objects for it. It also doesn't care about whether you use raw PHP or Smarty at the view layer, just that it should make some object available under some predetermined names for it. All the while the view layer doesn't even need to know there is a controller layer - only that it gets called with the data to display ready under the abovementioned names provided by /something/.
As frameworks templates go, I find the MVC pattern to be one of the most "loosely coupled" ways of building an application.
Think of the relationships like interfaces, or contracts between the parts of the application. The Model promises to make this data available to the View and the Controller. No one cares exactly how the Model does that. It can read and write from a typical DBMS, like MySQL, from flat files, from external data sources like ActiveResource, as long as it fulfills its end of the deal.
The Controller promises to make certain data available to the View, and relies on the Model to fulfill its promises. The view doesn't care how the Controller does it.
The View assumes that the Models and the Controllers will keep their promises, and can then be developed in a vacuum. The Model and Controller don't care if the view is generating XML, XHTML, JSON, YAML, plaintext, etc. They are holding up their end of the contracts.
And, of course, the View and the Controller need to agree that certain things exist. A View without some corresponding Controller activity might work fine, but could never be used. Even if the Controller doesn't do anything, as might be the case in static pages:
<?php
class StaticController extends ApplicationController
{
/**
* Displays our "about" page.
*/
public function about ()
{
$this->title = 'About Our Organization';
}
}
Then the associated View can just contain static text. (Yes, I have implemented things like this before. It's nice to hand a static View to someone else and say "Just write on this.")
If you look at the relationships between the M, V, and C as contracts or interfaces, MVC suddenly looks very "loosely coupled." Be wary of the lure of stand-alone PHP files. Once you start including and requiring a half-dozen .inc files, or mixing your application logic with your display (usually HTML) you may have coupled the individual pages more loosely, but in the process made a mess of the important aspects.
<?php
/**
* Display a user's profile
*/
require_once 'db.php';
$id = $db->real_escape_string($_GET['id']);
$user_res = $db->query("SELECT name,age FROM users WHERE id = $id;");
$user = $user_res->fetch_assoc();
include 'header.php';
?>
<h1><?php echo $user['name']; ?>'s Profile</h1>
<p><?php echo $user['name']; ?> is <?php echo $user['age']; ?> years old!</p>
<?php
include 'footer.php';
?>
Yeah, "profile.php" and "index.php" are completely unrelated, but at what cost?
Edit: In response to your edit: Push for MVC. You say you have "half-programmers," and I'm not sure which half (do you have front-end people who are good at HTML and CSS but not at server-side? writers with some programming experience?) but with an MVC framework, you can hand them just the views, and say "work on this part."
I have to say that I don't really see your problem with MVC, since your already using templates anyway. I kind of think of it as the pattern that evolves naturally when you try to add structure to an application.
When people first start developing PHP application, the code is usually one big mess. Presentation logic is mixed with business logic which is mixed with database logic. The next step that people usually take is to start using some kind of templating approach. Whether this involves a specialized template language such as smarty or just separating out the presentation markup into a separate file isn't really important.
After this most of us discovers that it's a good idea to use dedicated functions or classes for the database access logic. This really doesn't have to be any more advanced than creating specialized functions for each commonly executed query and placing all those functions in a common include file.
This all seems very natural to me, and I don't believe that it's very controversial. But, at this point you're basicly already using an MVC approach. Everything beyond this is just more or less sophisticated attempts to eliminate the need to rewrite commonly used code.
I understand that this might not be what to you wanted to hear, but I think you should re-evaluate MVC. There's a countless number of implementations, and if it's really the case that none of them suits your needs, then you could always write your own and more basic implementation.
Look at it this way: Since you're already using a template language you'll typically need to create first a regular PHP file, and then a templare file each time you create a new page. MVC doesn't have to be any more advanced than this, and in many cases it isn't. It might even be that all you really need to do is to investigate more sophisticated approaches for handeling data access and add it to your current system.
The fact that you have to create a new Model and Controller Action when you need a new page I don't think means that your M, V, and C layers are tightly coupled. This is just the separation of concerns and contributes to a decoupled system.
That said, it is quite possible to royally screw up the intent of MVC (and I've worked on an app like this) and make it make the components tightly coupled. For instance, a site might put the 'rendering engine' directly in the Controller layer. This would obviously add more coupling. Instead a good MVC will be designed so that the controller is only aware of the name of the view to use and then pass that name to the separate rendering engine.
Another example of bad design in an MVC is when the views have URLs hard-coded into them. This is the job of the Routing engine. The view should only be aware of the action that needs to be called and the parameter that action needs. The Routing engine will then provide the correct URL.
Zend framework is very loosely coupled and is very good. Check it out:
http://framework.zend.com
This article might be of use too:
http://blog.fedecarg.com/2009/02/22/zend-framework-the-cost-of-flexibility-is-complexity/
You can try code Igniter. Its very easy to learn and does not strictly adopt MVC whilst giving your code good structure.
Code Igniter and Kohana (a CI descendent) are OK, but also loosely MVC. I like the simple php framework. It doesn't get in your way and it provides the important stuff, without forcing a structure or complicated conventions on you.
Ah... good old MVC arguments.
I have to maintain a multi-faceted PHP application, pieces of which are written "MVC" style, but not all. Worse, different parts have different ways of doing MVC, all of which are homegrown. And some pages just do it all themselves.
The main problem is not that there is a diversity in framework code, but that the coders clearly did not understand how to abstract APIs. IMO, ths is the biggest problem with MVC frameworks. Almost all of the code I have to work with uses "models" as places to put functions. It is a nightmare to maintain.
To make this maintainable, IME you need a few things:
A distinct and well-defined data-access layer, the API boundary of which looks after retrieving and storing persistent storage and very little else.
I don't like to use the term "model" for that because that is contentious. Whatever calls that layer should not care how the data is stored, should not even be worrying about things like database handles: that is all the job of the data-access layer.
A dispatcher that is very light and doesn't do any magic outside of just dispatching.
Now you can put everything else in one place that accepts requests and parameters, probably normalised and error checked from the dispatcher, fetches the data (usually as objects) it needs, makes the changes it needs to do, saves the data it needs to, hands the data is needs to display to the view. Two hundred lines of code plodding through the task works for this step. You don't need to hive off bits into functions in another file that are called from nowhere else. You can even put the view on the end of this file! Idealism is nice to aspire to but pragmatism needs a look-in because this is maintainable.
(Okay, rant over... )
PHP's lack of enforcing a framework means that the best frameworks do what PHP does: they stay out of the way. Some of the most maintainable code I've worked on had a single require() statement at the top, did all the data-manipulation with data objects (no SQL in sight), then output HTML surrounded by template functions, with form control being done by a consistent function API.
I am trying to create simple php framework .But i am not sure about class structure for example which classes should extend to which classes .Firsly i am know that some basic classes such as Router , View classes have to access some basic data such as requested url or requested ccontroller and action so how can i import basic data to these classes .If my question is not clear please explain your own experiances and ideas about frameworks.or if you know please talk about known framewoks such as zend , cakephp or symfony
There is no best class structure. Depends on what you are trying to do. Do you mean purest MVC design? Most testable? Most easy to understand?
There is a simple rule of thumb:
Either you have a need that the standard frameworks can not fulfill
or you should use a good standard framework that does what you need.
In the first case the restriction will be the driving aspect in your design.
There are no general design rule for class structures in frameworks. But try to keep this in mind, if you decide to write your own one:
Minimize dependencies between modules
Always try to give default values
Try to minimize the overhead
Talk a lot with peers about it to find flaws early.
If you've never worked in someone else's framework you will have no idea what ideas work for you and what don't. If you've only ever worked with dis-organised spaghetti code, then you will have some idea of what makes sense for you. If you've made substantial re-organisation to dis-organised spaghetti code in more than one unrelated project, you should have a good idea of how you think in building a framework. :-)
If you don't have a firm idea of how you want to write a framework, but you want to write one, I think you need to start with nothing and build it organically. However, you should have some idea how you want it to look like, even if it's something as silly as where you want the include files to live. In other words, all you need is a starting point. Then it's a matter of re-factoring ugliness as you encounter it. Before long, you will have a database handler, a dispatch mechanism, perhaps a data access layer, just maybe even a templating system!
Responding to #MrFox, though, you should be aware of dangerous dependancies. Obviously a data access layer will depend on a database handler; so what you don't want is for your database handler to depend on your data access layer. In fact, you don't want them to have intimate knowledge of each other, either. It should be a reasonably "black-box" interface.
Also, a number of frameworks try to build "one" object heirarchy. This means they think an Action is-a Model is-a Database Handler. I personally have problems with this mis-applied abstraction, so this is a heads-up to not be afraid to spurn this idea if it doesn't work for you, either. As #Tyndall said, there's no one, single "right" way to do it.