Wiley Building PHP Applications with Symfony, CakePHP, and Zend Framework
Contents
1. gt code snippet singleton Test php The output of this code will look like this Customer_1 wants to rent the car Customer_1 says I drive Dodge Magnum really fast Customer_2 wants to rent the car Customer_2 says I can t rent this car Customer_1 returned the car DESIGN PATTERNS INWEB FRAMEWORKS 19 Customer_2 wants to rent the car Again Customer_2 says I drive Dodge Magnum really fast The Singleton pattern is used often in other design patterns such as Prototype State Abstract Factory or Facade Apart from that it can be used in all classes where you need a single instance with global access but there is no way to assign it to another object and perhaps you can also benefit from initialization on the first use Be wary though because it is easy to over use Singletons and they may be dangerous just like global variables Another problem with Singletons is that they carry their state throughout the execution of the program which seriously harms unit testing Some experts even argue that Singleton is a bad idea and it generally should be avoided Frameworks use Singletons for various reasons One of them is storing user data for security pur poses You want to have a single instance of a user that holds authentication data and make sure that no second instance can be created This approach is represented for example by the sfGuard class of Symfony Prototype The Prototype pattern is useful when y2. 2 0 versions which address all previously mentioned problems Advantages When web application frameworks are useful gt For more or less standard projects with dynamic content like social networking online stores news portals and so on gt For easily scalable applications that can grow from start up to worldwide popular services without need for big changes in code 4 CHAPTER1 INTRODUCING SYMFONY CAKEPHP AND ZEND FRAMEWORK For producing consecutive apps in which modularity and reusability of pieces of code like controllers and views may be helpful For real world development with deadlines rotating staff and fitful customers If you are or want to be a professional web developer so learning how to work with frame works is not an excessive effort As you can see this applies to most commercial web applications that connect to a database and allow its users to create and modify its content Therefore programming with web app frameworks becomes a standard and common practice in the web development world Disadvantages When you should consider development without any frameworks at all gt Purely informative web pages without user created content for example an artist s portfolio with fancy graphics Small projects with limited database connection that wouldn t benefit much from frame works code generation Really big projects that additionally need extreme performance like the Google suite you
3. gt drivesCar FALSE 18 CHAPTER1 INTRODUCING SYMFONY CAKEPHP AND ZEND FRAMEWORK else Sthis gt drivesCar TRUE function returnCar Sthis gt rentedCar gt returnCar this gt rentedCar function getMakeAndModel if TRUE S this gt drivesCar return I drive this gt rentedCar gt getMakeAndModel really fast else return I can t rent this car gt code snippet singleton Customer class php We can test these classes with the following code It creates two customers who both want to rent the car at the same time But the second one will have to wait until the car is returned lt php include_once Customer class php gt SCustomer_1 new Customer iar SCustomer_2 new Customer Wrox com echo Customer_1l wants to rent the car lt br gt SCustomer_1 gt rentCar echo Customer_1 says Customer_1 gt getMakeAndModel lt br gt echo lt br gt echo Customer_2 wants to rent the car lt br gt SCustomer_2 gt rentCar echo Customer_2 says Customer_2 gt getMakeAndModel lt br gt echo lt br gt SCustomer_1 gt returnCar echo Customer_1 returned the car lt br gt echo lt br gt echo Customer_2 wants to rent the car Again lt br gt SCustomer_2 gt rentCar echo Customer_2 says Customer_2 gt getMakeAndModel lt br gt echo lt br gt
4. http kohanaphp com Kohana is a community supported offshoot of CodeIgniter In contrast with Codelgniter Kohana is designed for PHPS and is fully object oriented While boasting higher elegance of code it still has all the qualities of Codelgniter It is extremely lightweight flexible and easy to learn The community behind Kohana is large and active so despite its young age it should be considered a stable and reliable framework Prado Started 2004 License revised BSD PHP versions 5 1 0 FIGURE 1 10 Prado logo Its logo is shown in Figure 1 10 Website www pradosoft com Prado stands for PHP Rapid Application Development Object oriented It enjoyed moderate popu larity some time ago but now its development seems a bit sluggish However it is still a mature framework well suited for most business applications One of its interesting features is that it nicely supports event driven programming It has some similarities with ASP NET 12 CHAPTER1 INTRODUCING SYMFONY CAKEPHP AND ZEND FRAMEWORK Yii Started 2008 A Lome 97 yliframework PHP versions 5 1 0 Its logo is shown in Figure 1 11 FIGURE 1 11 Yii logo Website www yiiframework com Yii was founded by a developer of Prado and it continues many of its conventions Yii is very fast leading in most benchmarks and extensible modular and strictly object oriented It has a rich set of features and decent documentation It uses no special configuratio
5. FIGURE 1 1 Search volumes of frameworks in various programming languages 6 CHAPTER1 INTRODUCING SYMFONY CAKEPHP AND ZEND FRAMEWORK OPEN SOURCE PHP WEB FRAMEWORKS Another question we want to answer is why we have chosen these three particular frameworks Are they really better in any way or are we biased or perhaps have some financial interest in promoting them Well starting with that last question we are completely independent open source enthusiasts and we wanted to compare free free as free speech software only so there is certainly no Evil Corporation behind us and nobody told us which frameworks to choose We answer the question of whether they re better than other frameworks in the following sections There were once closed source PHP frameworks as well but due to widespread success of the free frameworks nowadays closed source frameworks are a thing of the past Comparison of Popular Interest We have chosen Symfony CakePHP and Zend Framework due to their popularity in the web devel opers community including our own experience in PHP We believe that open source programming tools show at least some correlation between their popularity and quality because they are used only if they are really useful In that way they are different from things like proprietary software or pop music in which quality can be easily replaced by aggressive marketing as the popularity gaining factor It turns out that th
6. as a an error message response to a request DESIGN PATTERNS IN WEB FRAMEWORKS 25 So how do you create such Chain of Responsibility The main idea of this pattern is to process a request by a list of consecutive handlers to avoid any hard wired mappings The initial client holds a reference only to the first element in the chain of handlers Then each handler holds a reference to the handler afterward The last handler must always accept the request to avoid passing it to a NULL value A good class structure supporting this behavioral pattern is shown in Figure 1 24 It consists of a parent Handler class that calls the handle method to delegate the request to the next concrete handler nextHandler This Handler class is subclassed by concrete handlers that try to do some thing with the request if they fail they call the handle method of their superclass nextHandler 4 Handler handle t nextHandler handle HandlerOne HandlerTwo handle FIGURE 1 24 Chain of Responsibility pattern structure Chain of Responsibility is commonly used for filters One example of filtering is when a user request is being processed First it checks whether the given controller exists or not If it doesn t exist a 404 error is displayed If it does exist the request is passed to the controller which handles it further It checks whether a user tries to access an unsecured page if i
7. design patterns are a generally practical means that make up for a lack in formal mechanisms Most often they are cre ated when programming languages do not provide abstract mechanisms that become undeniably useful during the development of real world applications A good analogy for design patterns is the game of chess A novice player needs just to know the rules It s like learning the basic syntax of a programming language Still knowing how a bishop moves doesn t make you a successful chess player just like knowing how to open braces doesn t make you a PHP programmer Skilled players are able to predict a few moves forward and respond with a winning scheme That s like an experienced programmer who can in fact produce working software As you begin to master the game of chess you begin to see patterns emerging You can barely glance at the chessboard to classify the situation into one of these patterns and provide a proven response both for present and future risks You can perceive these patterns just intuitively or you may try to name them It s the same with software design patterns when you are truly proficient you use them all the time There is a good chance that you have used some of them without even knowing it Naming design patterns is not necessary but is indeed good for two things First is an aid for think ing with patterns because when you name something abstract it is much easier to implement it in practice
8. extremely flexible with extensive plug in support It has many truly experi mental and innovative functions like a filter system and an integrated test suite Lithium Started 2009 License BSD PHP versions 5 3 The second search result Google showed us for Lithium framework is a page titled CakePHP is dead Lithium was born This claim is still far from true however with the advantages provided by Lithium s support for PHP 5 3 Lithium may really endanger CakePHP in the future unless the latter takes immediate action OPEN SOURCE PHP WEB FRAMEWORKS 11 Agavi Started 2005 License LGPL PHP versions 5 2 0 recommended 5 2 8 Its logo is shown in Figure 1 8 Website www agavi org Like Symfony Agavi is based on the Mojavi framework It was started in 2005 but the 1 0 0 version was worked upon until early 2009 The source code is very polished and sometimes called the best written MVC OOP framework However it has not gained much popularity perhaps due to FIGURE 1 8 Agavi logo scarce documentation It was never meant to be popular The authors stress that Agavi is not a website construction kit but a serious framework built with power and extensibility in mind Its target applications are long term specialist projects that need full control of their developers Kohana Started 2007 License BSD RUIjGijd PHP versions 5 2 3 FIGURE 1 9 Kohana logo Its logo is shown in Figure 1 9 Website
9. is a Singleton representing one concrete specimen of a Dodge Magnum car ina car rental business The __construct function is the constructor of this class Note that it is set to private to prevent usage from outside of the class The double underscore indicates that __construct is one of the magic functions in PHP special functions provided by the language and declaring the constructor in a class will override the default one CarSingleton does provide an interface for renting and returning the car as well as pretty obvi ous getters The rentcar function checks first whether the car is already rented This is not part of the Singleton pattern but is important for the logic of our example If the car wasn t rented the function checks if the car variable is NULL before returning it If it equals NULL it is constructed before the first use Thus rentCar corresponds to the instance method of the design pattern The Customer class in the following example represents a person who uses the services of the car rental business He can rent the car there is only one return it and tell the make and model of the car provided that he drives it at the moment lt php include_once CarSingleton class php class Customer Avaliable for private rentedCar Wrox com private drivesCar FALSE function __construct function rentCar Sthis gt rentedCar CarSingleton rentCar if this gt rentedCar NULL Sthis
10. loads data from the Model and delivers it to the View Most so called MVC frameworks follow the MVP pattern While it is not bad itself because MVP seems even better suited to the task this naming convention may be somewhat confusing As long as MVP is derived directly from MVC it is not a big problem so in this book we will follow the names 16 CHAPTER1 INTRODUCING SYMFONY CAKEPHP AND ZEND FRAMEWORK conferred by the authors of the frameworks So we will call all frameworks Model View Controller even if the Controller does the majority of data transferring work Data Manipulation and Delivery Updates FIGURE 1 18 Model View Presenter pattern Overview of Other Design Patterns Design patterns can be divided into creational behavioral and structural patterns Full description of all design patterns is well beyond the scope of this book but you can find it in the most influ ential book on this subject Design Patterns Elements of Reusable Object Oriented Software by Erich Gamma Richard Helm Ralph Johnson and John Vlissides the Gang Of Four However we want to provide you with just a short overview of design patterns that are commonly used in web frameworks Singleton This design pattern which is so trivial it is often called an antipattern is very useful The purpose of the Singleton pattern is to ensure that a class has only one instance and to make this instance globally acces sible Whenever another object
11. we have found to be used successfully to develop web applications Codelgniter Started 2006 License modified BSD PHP versions 4 3 2 Its logo is shown in Figure 1 6 Website http codeigniter com Codelgniter is developed and maintained by a privately owned software development company Ellis Labs It is focused on hav ing a very small footprint while allowing a big increase in perfor mance It follows the MVC pattern only partially for the models are FIGURE 1 6 Codelgniter logo optional It is loosely coupled and in the words of Rasmus Lerdorf it s the least like a framework Its lightweight approach has earned a wide recognition in the developers community but it is sometimes criticized for conformance with PHP 4 Codelgniter is a good choice for less complex web applications that would benefit from using a framework but the heavier ones would either hinder the applications performance with excessive features or their configuration would take too much time The structural simplicity of Codelgniter makes it also a frequent pick by beginners who choose it as learning platform before moving to a A Lithium Its logo is shown in Figure 1 7 Website FIGURE 1 7 Lithium logo http lithify me Lithium took all the best that CakePHP had to offer and moved it to PHP 5 3 First it was a branch of CakePHP called Cake3 now it is a separate project run by some former CakePHP developers It is lightweight fast and
12. Introducing Symfony CakePHP and Zend Framework An invasion of armies can be resisted but not an idea whose time has come VicTOR HuGo WHAT S IN THIS CHAPTER gt General discussion on frameworks gt Introducing popular PHP frameworks gt Design patterns Everyone knows that all web applications have some things in common They have users who can register login and interact Interaction is carried out mostly through validated and secured forms and results are stored in various databases The databases are then searched data is processed and data is presented back to the user often according to his locale If only you could extract these patterns as some kind of abstractions and transport them into further applications the development process would be much faster This task obviously can be done Moreover it can be done in many different ways and in almost any programming language That s why there are so many brilliant solutions that make web development faster and easier In this book we present three of them Symfony CakePHP and Zend Framework They do not only push the development process to the extremes in terms of rapidity but also provide massive amounts of advanced features that have become a must in the world of Web 2 0 applications 2 CHAPTER1 INTRODUCING SYMFONY CAKEPHP AND ZEND FRAMEWORK WHAT ARE WEB APPLICATION FRAMEWORKS AND HOW ARE THEY USED A web application framework is a bunch o
13. Then you may further analyze this pattern draw diagrams of it and take full advantage of it And the other thing is that you can share your experience Chess players love to talk about various openings and gambits and programmers can learn a lot by exchanging knowledge of design patterns as well And even more important if you want another programmer to add some functionality to a fixed class and then tell him to use the Decorator pattern you can expect that it will be done the way you want it rather than with a random makeshift solution Thus design patterns have a great potential for preventing future problems Model View Controller as the Main Structural Design Pattern Web frameworks take advantage of most if not all design patterns However MVC is the abso lute structural backbone of all frameworks The main idea of MVC is dividing the application into three layers DESIGN PATTERNS IN WEB FRAMEWORKS 15 gt Model Represents the business logic of the application It is more than just the raw data the Model has to represent the structure of data with all relationships and dependencies It may comprise one or more classes that correspond to logic objects of the application and provide an interface for manipulating them The Model is the only layer that uses persistent storage It should completely encapsulate all database connections The model should also notify the View when its internal state changes so the View can be refre
14. braries frameworks even though they do not invoke developers code There WHAT ARE WEB APPLICATION FRAMEWORKS AND HOW ARE THEY USED 3 is nothing wrong with a piece of code being a library as it is just a different entity And there are also some bad frameworks that damage the reputation of the good ones basically you can take any half done application release it and call it a framework These two software groups just behave differently and should not be confused The application architecture utilized by frameworks is called inversion of control because the data flow is inverted compared to ordinary procedural programming It is also referred to as The Hollywood Principle Don t call us we ll call you This corresponds to third party code calling developer s code The main reason behind it is to make the high level components less dependent on their subsystems High level components pass the control to low level components who themselves decide how they should work and when to respond A good example is the difference between a command line program which stops and then asks the user for input and a program with a win dowed user interface in which the user can click any button and then the window manager calls the program instead Some frameworks such as Zend Framework or Codelgniter follow loosely coupled architecture which means that their components are less dependent on each other and may be used separately mor
15. d as search volume in the Google search engine in the Computers amp Electronics category The figure was cre ated with Google Insights for Search which is a more advanced form of the well known Google Trends tool You can check these search terms yourself to obtain results beyond mid 2010 that s when this book was written at the website www google com insights search Compare by Search terms Filter Searchtems Tip Use the minus sign to exclude terms wimbledon tennis Web Search a Locations cakePHP symfony zend framework codeigniter Worldwide el Time Ranges turbogears pylons grok web2py django reinhardt 2004 present a e mbyonmis a t spring framework apache struts wavemaker Computers amp Electronics v ASP NET MVC monorail dotnetnuke openrasta Search Web Search Interest cakephptsymfony zend framewo Totals turbogearstpylonstgrok web2p ruby on rails spring framework tapache stru cakephpt synfonyze a 40 asp net mvctmonorailtdotnetn turbogears pylons men 27 Worldwide 2004 present ruby on rails ee 52 All Categories gt Computers amp Electronics spring framework a _ 32 Subcategories Programming Software Enterprise Technology Hardware Networking more asp net mvc monora mumm 20 Interest over time T Forecast Interest level Growth relative to the Computers amp Electronics category Leam what these numbers mean Python Asa
16. e library style Loosely coupled frameworks do not provide development as rapidly as those fol lowing a tighter framework architecture and Model View Controller MVC pattern however such an approach allows more flexibility and control over code When You Should Use a Framework and When You Should Not Frameworks are not the cure for all programming problems Putting aside today s awesome state of development you should always remember how frameworks were created a few years ago Most of them were more or less unoptimized junk created by one guy to help him speed up his development process without much care for documentation elegance ease of use or even read ability of his code Then another group of guys took this code and bloated it with a patchwork of extra functionalities barely consistent with the original code Then it became apparent that this whole lot needs a solid cleanup in order to be usable but this would mean either rewriting it from scratch or packaging code in additional wrapper classes further increasing its unnecessary complexity Of course today the disorganized origin of frameworks is not as evident as before because the qual ity of code has risen considerably But still that s why most beefed up frameworks have performance issues That s why they are not always easy to learn And that s why new ones emerge to cover up weaknesses of older ones And finally that s why major frameworks provide completely rewritten
17. e public interest in web frameworks can be measured quite objectively Figure 1 2 shows search volumes for various PHP frameworks in Google Insights for Search You can easily see that there are four leading competitors All the others combined are less popular than any one of these four The Lithium and Prado frameworks have been deliberately omitted because their names are nonunique which generates false positives in trends We have checked these names in specific categories and found that they are not significant as search terms either When users search for information on a framework the search results usually reflect talk about it on various blogs and forums items about learning this technology and finally developing applica tions using it So public interest in a web framework results in real long term use of it Codelgniter was really problematic for us We had a long debate whether it should be included as one of the main frameworks Perhaps now it is as frequently searched for as Symfony or CakePHP but what matters more is the area under the graph because it reflects how many people have found the answers they sought and have probably used this knowledge for their projects Of course this graph shows nothing more than search volume and when you see such fast growth it is hard to distinguish a long lasting trend from temporary hype We know that Codelgniter is really good so it is definitely more than a fad and perhaps in a year or two
18. f source code organized into a certain architecture that can be used for rapid development of web applications You can think of frameworks as half produced applications that you can extend and form to make them take shape according to your needs Well that means half your work has already been done but for some it is as much a blessing as a curse because this work was done in a particular way without your supervision Thus all frameworks are either stained with a coding methodology and naming and structural conventions or if they try to avoid these restrictions they need to be heavily configured by you This either reduces their flexibility or makes their learning curve significantly steeper And if you really want to escape from these problems toward a more library like approach you have to sacri fice some development speed You can see that frameworks are all about tradeoffs That s why it is really good to take a look at many frameworks and compare their differences Perhaps one of them offers conventions that you would use as good practices anyway Perhaps you have nothing against some initial configuration that allows you to be rapid and flexible at the same time And maybe you want just a library of powerful components to link together by your self The choice is yours and if you find a way to mitigate their disadvantages you can fully enjoy the greatest benefit of all frameworks truly rapid development Further advantages of framew
19. g released in late 2010 It offers various new features and greatly enhanced performance CakePHP Started 2005 License MIT PHP versions 4 3 2 Its logo is shown in Figure 1 4 Website http cakephp org FIGURE 1 4 CakePHP logo OPEN SOURCE PHP WEB FRAMEWORKS 9 CakePHP was started in 2005 by the effort of Polish web developer Micha Tatarynowicz Heavily inspired by Ruby on Rails CakePHP is an entirely community driven open source project with lead developer Larry Masters aka PhpNut The next major release of CakePHP has also been announced but its release date is still unknown The most important goals of CakePHP are its friendliness development speed and ease of use And it really excels in that Works out of the box or oven with no configuration It has perfect docu mentation with working examples for most of its features And it has really a lot of features to use That allows the most rapid development with a smaller amount of code One of the most controversial features of CakePHP is its compatibility with PHP4 While once it allowed deployment on old cheap hosts that did not support PHPS now it is more a drawback hindering CakePHP s development Fortunately version 2 0 will use PHP 5 3 There are also reports of CakePHP s really bad performance but they were mainly due to disabled caching by default Zend Framework Started 2005 License new BSD PHP versions 5 2 4 since ZF 1 7 0 ap Its lo
20. go is shown in Figure 1 5 Website http fr d framework zend com FIGURE 1 5 Zend Framework logo Zend Framework is sponsored by the U S Israeli company Zend Technologies Ltd which was cofounded by Andi Gutmans and Zeev Suraski the core developers of PHP Strategic partners of Zend Technologies Ltd include Adobe IBM Google and Microsoft The company offers various commercial products however Zend Framework is an open source project released under the corporate friendly new BSD license ZF is meant to be simple component based and loosely coupled This means that it is a library of components which you can use as you wish and usage of MVC architecture is optional This lowers the learning curve and increases its flexibility The documentation is great and the source code is of very high quality both because it s fully object oriented and thoroughly unit tested Zend announced an upcoming 2 0 version as well but its release date is still unknown Other Frameworks There are hundreds of PHP frameworks This is not an exaggeration if you count all of them including ancient and already abandoned projects as well as brilliant younger startups and some useless short lived junk The web app market is a big one but the amount of PHP tools is 10 CHAPTER1 INTRODUCING SYMFONY CAKEPHP AND ZEND FRAMEWORK disproportionally huge and perhaps somewhat excessive Here is an overview of a few more notable ones that
21. he best choice when starting a new project but there are still numerous successful applications that were built with it It has contributed greatly to the development of all other PHP frameworks OPEN SOURCE PHP WEB FRAMEWORKS 13 Qcodo Started 2005 License MIT Acada PHP DEVELOPMENT FRAMEWORK FIGURE 1 14 Qcodo logo PHP versions 5 x Its logo is shown in Figure 1 14 Website www qcodo com Qcodo is an MVC framework that excels in code generation from database design It has a very powerful code generator that analyzes the structure of the data model and creates PHP object code and also HTML pages for database manipulation Perhaps this is not one of the more popular frameworks you are likely to hear about during a casual conversation but several top institutions including NASA have applied it for their projects Qcodo was created by Mike Ho of QuasIdea Development and is now developed by an active community It also has a completely community driven fork called Qcube Solar Started 2005 License New BSD An fs PHP versions 5 2 O S O LAR WwW Poe WOTK EO Its logo is shown in Figure 1 15 Website http solarphp com FIGURE 1 15 Solar Framework logo SOLAR stands for Simple Object Library and Application Repository Its structure and naming conventions are similar to those of Zend Framework One of the biggest differences is how you construct objects all are created with a unified constructor and configu
22. ic leather seats sunroof better audio or GPS satellite navigation However the basic interface remains the same you can drive this car and feel good doing it When you face such alternatives the number of possible combinations rises really fast Figure 1 21 shows some combinations for just three improvements described as inheritance hierarchy Car drive Car_with_AutoTransmission Car_with_GPS Car_with_Sunroof Car_with_AutoTrasmission_and_Sunroof Car_with_AutoTransmission_and_Sunroof_and_GPS FIGURE 1 21 Nasty inheritance hierarchy The answer to this problem is the Decorator pattern The Decorator is a class that shares the inter face with the decorated class in our example it is the basic car It encapsulates an instance of the 22 CHAPTER1 INTRODUCING SYMFONY CAKEPHP AND ZEND FRAMEWORK decorated object and extends its responsibilities dynamically It is like putting a gift into a solid box and then wrapping it with colorful paper it is still a gift but durable and decorated The inheri tance structure of the Decorator pattern is presented in Figure 1 22 interface Driveable drive Car CarDecorator drive drive AutoTransmissionDecorator GPSDecorator SunroofDecorator FIGURE 1 22 More reasonable inheritance hierarchy with Decorator You ca
23. it will have its place among the leading web tools We finally agreed that three men against four frameworks is not an equal fight We have not com pletely forsaken Codelgniter though its features are described along with Lithium and Agavi in Appendix B where a simple application is developed using each one of them OPEN SOURCE PHP WEB FRAMEWORKS 7 Compare by Search terms Filter Searchterms Use quotation marks to match an exact phrase table tennis Web Search Locations cakePHP Worldwide Time Ranges symfony a re E Resa ee Jan 2006 z Jun 2010 Reset codeigniter All Categories X kohana agavi qcodo akelos php on trax Search iai Totals Web Search Interest cakephp symfony zend framework codeigniter cakephp TT kohanatagavitqcodotakelos tph symfony 53 Worldwide Jan 2006 Jun 2010 zend framework 49 Categories Computers amp Electronics Internet Travel Local Home amp Garden Food amp Drink codeigniter eee 29 kohana agavi qcodo mmm 14 Interest over time E News headlines Leam what these mbers mean 2006 i 2007 2008 2009 The last value on the graph is based on partial data and may change Learn more FIGURE 1 2 Comparison of search volumes of different PHP frameworks The First Look The first look at the frameworks really gives us little information on their individual features Their websites just try to impress y
24. ivide web content into adequate pieces turn them into separate web pages and then traverse through them
25. n or templating language so you don t have to learn anything apart from object oriented PHP to use it Also unlike many other frameworks it follows pure MVC architecture with data being sent directly from Model to View Akelos Started 2006 License LGPL Pe Ake O S PHP versions 4 or 5 FIGURE 1 12 Akelos 2 logo Its logo is shown in Figure 1 12 Website http www akelos org http github com bermi akelos While all PHP frameworks are more or less inspired by Ruby on Rails Akelos aims to be its direct port It is focused on internationalization provides multilingual models and views as well as Unicode sup port without extensions and can run on low cost shared hostings that s why it has support for PHP4 The author of Akelos announced the completely rewritten Akelos 2 It drops support for PHP4 and uses autoloading and lazier strategies for loading functionality Its hallmarks will be advanced rout ing methods and strong REST orientation REST is described in Chapter 12 It is to be released in late 2010 and it looks very promising Seagull Started 2001 License BSD ays f Seagu Il APPLICATION FRAMEWORK PHP versions 4 3 11 FIGURE 1 13 Seagull logo Its logo is shown in Figure 1 13 Website http seagullproject org Seagull is a true veteran among PHP frameworks it was founded in 2001 Years of development made it solid stable and tested It is no longer actively developed so perhaps it is not t
26. n put the decorated object into other Decorators without limitations This way you can add as many optional modules as you wish Decorators can have their own inheritance hierarchy and within this hierarchy they encapsulate the core object recursively The code below creates a standard car class without optional equipment lt php D class Car public gearMessage Remember to shift up Available for i i download on public comfortMessage standard Wrox com function drive return Accelerating this gt gearMessage Driving comfort is this gt comfortMessage gt code snippet decorator Car class php The following classes are responsible for extending the functionality of the car The first one CarDecorator is the first level of wrapping It stores the car variable and a copy of ScomfortMessage This variable will be changed by a Decorator so we create a copy to avoid changing the original car object On the other hand gearMessage is changed internally The drive function is also sub classed to use the proper variables car gt model and Sthis gt gearMessage because we want to access the core object here but this gt comfortMessage because we want to use the amended value Second level Decorators wrapping the CarDecorator are used to install optional components as shown below AutomaticTransmissionDecorator installs the s gearMessage directly into the core Scar but GPSDecorator is installed in
27. needs access to the Singleton it calls a static globally accessible function that returns reference to the single instance You can see the structure of the Singleton in Figure 1 19 Singleton Client gt static instance FIGURE 1 19 Singleton pattern structure The trick behind Singleton is to make the instance and all its constructors private So there is no way to demand creation of a Singleton class instance How is the first and only instance cre ated The instance method checks whether this object already exists if not it creates the single instance before returning it Let s look at how this works with the PHP code lt php class CarSingleton gt private make Dodge hoa pe tr private model Magnum Wrox com private static car NULL DESIGN PATTERNS IN WEB FRAMEWORKS 17 private static isRented FALSE private function __construct static function rentCar if FALSE self SisRented if NULL self car self car new CarSingleton self SisRented TRUE return self car else return NULL function returnCar CarSingleton carReturned self SisRented FALSE function getMake return this gt make function getModel return this gt model function getMakeAndModel return this gt getMake this gt getModel code snippet singleton CarSingleton class php The class in the preceding code
28. nput exceeds the field area Chain of Responsibility The three preceding design patterns concerned object creation and inheritance structure Chain of Responsibility is a pattern of another kind because it applies to the behavior of objects Its main intent is to decouple the sender of a request from its receiver Let s see how it works with an automotive example Imagine that there is an emergency on the road and you Request Client need to quickly stop the car In other words stop is the emitted request In most cases hitting the brake pedal is a at ee sufficient solution but there are rare cases when you find Processing the brakes broken that s when Chain of Responsibility element comes in handy If brakes cannot handle the request they pass it to the handbrake If for any reason the handbrake is i Processing i i element broken too and you are going to hit the obstacle at least airbags should open potentially saving your life Airbags ITT are the most generic solution to most road emergencies N They are less preferred than more specialized solutions braking evading but still better than nothing if those Processing maneuvers fail It s the same with your applications it is element better to give the request a chain of potential handlers as shown in Figure 1 23 instead of letting it fail without even FIGURE 1 23 Chain of Responsibility
29. or various Java WHAT ARE WEB APPLICATION FRAMEWORKS AND HOW ARE THEY USED 5 technologies Then in 2005 there was a boom of Ruby Everyone was amazed with the elegance of this programming language and Ruby on Rails the central piece of software ever written in Ruby was claimed to be the ultimate web applications framework Soon clones of Ruby on Rails began popping out That s how Python s Django and Turbogears as well as all PHP frameworks were born In 2004 PHPS was released It was neat and object oriented If somebody still wrote old styled HTML mixed with pieces of PHP script it was only his choice and the programming language no longer was to blame It took some time but people gradually considered PHP as a disciplined and professional tool Together with the modern MVC paradigm and features styled after other frame works PHP begun its amazing way to the top of web development applications After a few years it became evident that Ruby on Rails had various limitations One important limitation was the low availability and high price of Ruby hostings while there was a lot of cheap hosting for PHP everywhere in the world There was also a great community that eagerly developed early PHP frameworks This resulted in an IT revolution that dethroned Ruby on Rails as the most popular framework and placed a council of PHP frameworks in its place Figure 1 1 illustrates the change in interest in various frameworks over time expresse
30. orks are elegance of code and minimizing the risk of programming errors Frameworks conform to the Don t Repeat Yourself DRY principle which means that they have all the pieces of logic coded only once in one place This rule forbids duplication of code especially copypasting This facilitates maintenance of code and prevents nasty errors Generally frameworks promote code reusability and other good programming practices wherever they can which is great for programmers who do not have enough knowledge or discipline to care for quality of code by themselves Another great feature is the clean organized look of links that can be done with URL rewriting which is supported by most frameworks Instead of animals php species cats amp breed maineco on type just animals cats mainecoon This is not only appealing to the eye but also very search engine optimization SEO friendly Framework versus Library The main difference between a library and a framework is that gt libraries are called from your code gt frameworks call your code In other words a framework in your application is a skeleton that you fill with features or serves as a platform on which you build your modules Whereas a library instead provides attachable modules on top of a platform made by yourself Some people perceive a framework as something better or more complete than a library so framework became a buzzword that is often overused That s why people call some li
31. ou need the flexibility of parameterized object creation and when you want to avoid using the new operator Object creation is done here by creating a parent class with an abstract clone method and a few subclasses implementing clone Each of these subclasses comes with one instantiated Prototype object which clones itself when you call for a new instance This results in easiness and flexibility of object creation you don t have to hard wire the concrete subclass name in your code Instead you can pass the name of the class as a string or refer ence to the appropriate Prototype This pattern also greatly supports deep copying of objects Instead of cloning the Prototype you can clone an existing object receiving an exact copy as the result You can even copy objects from a container with mixed objects of various subclasses The only requirement is that they implement the clone interface Copying objects this way is much faster than creating objects with new and assigning values A general diagram of this pattern is shown in Figure 1 20 CarDealer CarPrototype gt CarPrototype order String model clone DodgePrototype SubaruPrototype clone clone FIGURE 1 20 Prototype pattern structure PHP has another magic function __clone does most of the work for you All you have to do in the following example is to create an abstract CarPrototype class and subclasses for different prod
32. ou with marketing descriptions and a list of features that vary little from one framework to another Symfony is a full stack framework a library of cohesive classes written in PHP It provides an architecture components and tools for developers to build complex web applications faster Choosing symfony allows you to release your applications earlier host and scale them without problem and maintain them over time with no surprise Symfony is based on experience It does not reinvent the wheel it uses most of the best practices of web development and integrates some great third party libraries CakePHP is a rapid development framework for PHP that provides an extensible architecture for developing maintaining and deploying applications Using commonly known design patterns like MVC and ORM within the convention over configuration paradigm CakePHP reduces development costs and helps developers write less code Extending the art amp spirit of PHP Zend Framework is based on simplicity object oriented best practices corporate friendly licensing and a rigorously 8 CHAPTER1 INTRODUCING SYMFONY CAKEPHP AND ZEND FRAMEWORK tested agile codebase Zend Framework is focused on building more secure reliable and modern Web 2 0 applications amp web services Now see whether you can spot three differences Well the websites are not really informative about unique features of their frameworks You can find more in vari
33. ous blogs and forums but still there is little verified data and general discussions tend to exchange purely personal opinions That is why we have written this book In fact the differences between frameworks are not really obvious and it takes some time and practical examples to see them and then harness them in busi ness solutions Let s begin with some most basic facts Symfony Started 2005 License MIT PHP versions symfony gt Symfony 1 4 PHP 5 2 4 gt Symfony 2 0 PHP 5 3 FIGURE 1 3 Symfony logo Its logo is shown in Figure 1 3 Website www symfony project org Symfony was produced in a French web development company Sensio Labs by Fabien Potencier First it was used for the development of its own applications and then in 2005 it was released as an open source project Its name was symfony but it is sometimes capitalized as we do in this book in order to make it more distinct Symfony was based on an ancient Mojavi MVC framework with some inevitable influences from Ruby on Rails It also integrated Propel Object Relational Mapper and took advantage of the YAML Ain t Markup Language YAML serialization standard for configuration and data model ing The default object relational mapping ORM solution has been later changed to Doctrine Today Symfony is one of the leading web frameworks It has a large active community and a lot of documentation mainly free e books Symfony 2 0 is bein
34. red with an array in a config file It has many helpful built in example applications PHP On Trax Started 2007 License GPL PHP versions 5 x Its logo is shown in Figure 1 16 Website www phpontrax com As the name cleverly suggests this framework was designed as an exact PHP copy of Ruby on Rails At least it was meant to be because it still lacks many features and it is highly unlikely that it FIGURE 1 16 PHP on Trax logo will finally realize this goal It is just one of many good looking frameworks that have eventually failed 14 CHAPTER1 INTRODUCING SYMFONY CAKEPHP AND ZEND FRAMEWORK DESIGN PATTERNS IN WEB FRAMEWORKS There are certain abstractions that can be transported between applications in order to make the development process faster This section takes a closer look at these abstractions and the way they shape the web application frameworks It is not absolutely necessary to understand design patterns in order to start working with frame works so if you are bored you can skip to the next chapter and come back here later However design patterns are fairly fundamental to these frameworks and application development as a whole so we insist that you really come back here if you decide to skip this section now What Is a Design Pattern The definition of design pattern states that it is a general solution to a commonly occurring problem in software design There is really not much more formal foundation because
35. rnal pointer to the first element function valid Returns true if the element under current key is valid Now every class implementing this interface can use the foreach structure The following snippet of code produces the same output as the previous for loop foreach S myArray as value echo value The abstraction behind this mechanism is the Iterator design pattern pictured in Figure 1 26 The Client application has access to two abstract classes Collection which is the aggregate object interface and TraversalAbstraction which is created by a corresponding Collection The underlying concrete collections can be as different as a List and a Map yet corresponding methods DESIGN PATTERNS IN WEB FRAMEWORKS 27 of traversal can be produced for both of them When client calls the next method different ordering algorithms are executed for List and for Map but in both cases a subsequent element is found Client Collection l createTraversalObject TraversalAbstraction ListCollection MapCollection TraversalAbstraction ESUS p irst createTraversalObject createTraversalObject next r isDone i v i ListTraversal ListTraversal rN i FIGURE 1 26 Iterator pattern structure In web frameworks the Iterator pattern is used mainly for pagination You need a uniform interface to d
36. shed gt View The output displayed to the user The most important thing is that the View never modifies the application data it only presents it There may be multiple Views for the same data such as traditional HTML PDF Flash or WML for mobile devices They should be interchangeable without modifying the other layers gt Controller The part of an application responsible for handling user interaction and taking all other actions The Controller should be created with simplicity in mind it should be the controlling part that uses methods provided by the Model and the View it shouldn t do everything by itself Figure 1 17 illustrates the relations between the three layers Data Manipulation Controller Data FIGURE 1 17 Model View Controller pattern MVC versus MVP MVC is an old design pattern dating back to the 1979 work Applications Programming in Smalltalk 80 How to use Model View Controller by Trygve Reenskaug Since that time it was often used in non web applications mostly graphical user interfaces in compiled languages like C or Java There it was easy and natural to implement an exact MVC pattern but for web applications it was somewhat modified Model View Presenter MVP shown in Figure 1 18 is a derivative of MVC It is a three tier appli cation structure where the Presenter acts as a middle layer between the View and the Model The Presenter differs from the Controller in that it
37. t s true it redirects the request to an SSL secured page Then it is checked for authentication and so forth State Sometimes you want a component to behave differently for various possible states of the application First define an abstract State class which is a common interface for various ConcreteStates All states provide a handle method that provides various behaviors of your component The context class is the core class that wraps a ConcreteState state object This design pattern makes sense when Context is a complete class that also provides state independent functionalities Otherwise simple subclassing of Context would be more efficient Context calls the state gt handle method when processing its own requests Context also has methods for switching between States Depending on which CconcreteState the state variable holds the state gt handle method provides different behaviors This can be regarded as emulation of a partial type change at runtime You can see a diagram of this pattern in Figure 1 25 The State pattern although rather simple is very useful for application development One example is database connection the database abstraction layer may change its behavior depending on the current connection state Another example can be the state of a transaction in an online store the 26 CHAPTER1 INTRODUCING SYMFONY CAKEPHP AND ZEND FRAMEWORK application may display different pages depending on which s
38. teps are needed to complete the transaction Context State request handle tate handl i state handlel ConcreteStateA ConcreteStateB handle handle FIGURE 1 25 State pattern structure Iterator There are many kinds of aggregate objects and many ways to traverse them One simple example is an array traversed by consecutive integers supplied to the array operator To print out a five element myArray you could use the following for i 0 i lt 4 i echo myArray i However this solution is not at all elegant First of all you have to take care of i variable values PHP is not C C so it is not catastrophic to call for myArray 100 here it will not return random trash from memory However it is still easy to skip some values with hard wired ranges Another problem is that such an approach exposes the underlying representation of this aggregation It makes the traversal procedure dependent on this specific representation and thus is not reusable Object oriented programming aims to encapsulate the internal structure of aggregate objects and provide a uniform safe and useful interface like this one provided by PHP interface Iterator function current Returns the value of element under current key function key Returns the current key function next Moves the internal pointer to the next element function rewind Moves the inte
39. ticTransmissionDecorator decorator Sgps new GPSDecorator decorator echo Driving standard car lt br gt echo car gt drive lt br gt Stransmission gt installAutomaticTransmission Sgps gt installGPS echo Driving fully decorated car lt br gt echo decorator gt drive lt br gt 24 CHAPTER1 INTRODUCING SYMFONY CAKEPHP AND ZEND FRAMEWORK echo Driving the car without decoration lt br gt echo car gt drive lt br gt 7 gt code snippet decorator Test php And the result will be the following Driving standard car Accelerating Remember to shift up Driving comfort is standard Driving fully decorated car Accelerating Auto transmission shifts up Driving comfort is very high Driving the car without decoration Accelerating Auto transmission shifts up Driving comfort is standard First we call the basic car model Next we install the optional equipment and call the drive function of the CarDecorator Finally we choose to drive the car not using the Decorator wrap ping Note that after calling the car then its transmission is still automatic That s because the Decorator changed it permanently Going back to frameworks the Decorator pattern is used among others for layouts and templates It is very useful for adding optional visual components or extending the user interface when new widgets are needed An example may be adding scrollbars when user i
40. to the CarDecorator instead Note that all decorators share the common interface and additionally provide specific installers DESIGN PATTERNS IN WEB FRAMEWORKS 23 2 Available for download on Wrox com lt php class CarDecorator protected car protected gearMessage protected comfortMessage public function _ construct Car car_in Sthis gt car car_in Sthis gt comfortMessage car_in gt comfortMessage function drive return Accelerating this gt car gt gearMessage Driving comfort is this gt comfortMessage class AutomaticTransmissionDecorator extends CarDecorator protected decorator public function _ construct CarDecorator decorator_in Sthis gt decorator decorator_in public function installAutomaticTransmission this gt decorator gt car gt gearMessage Auto transmission shifts up class GPSDecorator extends CarDecorator protected decorator public function __construct CarDecorator decorator_in Sthis gt decorator decorator_in public function installGPS Sthis gt decorator gt comfortMessage very high 2 gt code snippet decorator CarDecorator class php We can test these classes with the following code J Available for download on Wrox com lt php include_once Car class php include_once CarDecorator class php Scar new Car Sdecorator new CarDecorator car Stransmission new Automa
41. ucers The __clone function is declared abstract so subclass methods are used by default when this method is called 20 CHAPTER1 INTRODUCING SYMFONY CAKEPHP AND ZEND FRAMEWORK Q Available for download on Wrox com Cars are quite an accurate example here because in real life a prototype is created by a manufac turer and then different models are based on this prototype and filled with unique features The following code tests the preceding classes First it creates two Prototype objects as showcase cars and then clones one of them to serve the customer Then the color can be picked by the uniform lt php abstract class CarPrototype protected model protected color abstract function __clone function getModel return this gt model function getColor return this gt color function setColor ScolorIn this gt color colorIn class DodgeCarPrototype extends CarPrototype function __construct Sthis gt model Dodge Magnum function __clone class SubaruCarPrototype extends CarPrototype function __construct Sthis gt model Subaru Outback function __clone 2 gt code snippet prototype CarPrototype class php interface O Available for download on Wrox com lt php include_once CarPrototype class php SdodgeProto new DodgeCarPrototype SsubaruProto new SubaruCarPrototype echo Which car do you want lt br gt Sc
42. ustomerDecision Subaru if ScustomerDecision Subaru ScustomersCar clone S subaruProto else ScustomersCar clone dodgeProto echo customersCar gt getModel lt br gt echo What color do you want lt br gt ScustomersCar gt setColor red DESIGN PATTERNS IN WEB FRAMEWORKS 21 echo Fine we will paint your customersCar gt getModel ScustomersCar gt getColor lt br gt gt code snippet prototype Test php The previous code will result in the following messages Which car do you want Subaru Outback What color do you want Fine we will paint your Subaru Outback red The Prototype pattern is used commonly in different modules of frameworks An example can be nesting of forms within forms in Symfony or the AppCont roller class of CakePHP Decorator Subclassing is a great mechanism but it has some serious limitations Suppose that you want to pro duce a car You put all your effort into designing a good yet affordable standard model of the car It is a complete design that defines the look and feel of this model and it is a reference for any possible modifications Then you seek to provide some optional equipment that improves the quality of the car and adds some new functionalities For example it may be all wheel drive instead of front wheel drive It may be automatic transmission instead of manual The car may also come in different trim levels with electr
43. would be using a compiled programming language for that rather than PHP anyway With limited hardware resources that call for top performance as well not really a likely scenario because programming costs are now always higher than hardware costs Specialist or experimental applications that may evolve in completely unknown direction or work with some custom solutions like interfaces for scientific experiments with an object oriented database When you really need and can afford total control over the code and evolution of the application When you want to create a web app but you or your co workers don t want or even worse cannot learn how to use a framework These conditions are generally fulfilled by three types of projects small static websites extremely specialist websites and failed websites Frameworks are created for development of common web applications with well known standard architecture Of course they may be greatly extended thanks to plug ins and modules but complete alteration of their structure may require much painful hacking so you should always check their capabilities with the design requirements of your project PHP versus Other Programming Languages PHP for many years has been a very popular programming language however it was commonly judged as unprofessional A stereotypical PHP developer was an undereducated freelancer pro ducing cheap low quality code Professionals were supposed to use Zope ASP
Download Pdf Manuals
Related Search