 | Level: Intermediate Nicholas Chase (ibmquestions@nicholaschase.com), Consultant, Backstop Media
27 Jun 2006 We programmers are a paradoxically lazy lot. By that, I mean
that we will spend hours, even days, creating something that allows us to
complete a task in 30 seconds instead of five minutes. So perhaps the creation
of the Zend Framework isn't much of a surprise. You mean you haven't heard of
the Zend Framework? Don't worry — you will. This article gives you a high-level view of the Zend Framework, explaining its general concepts and preparing you for the rest of this "Understanding the Zend Framework" series, which goes into the details by chronicling the creation of a new online RSS/Atom feed reader. We won't do much coding in this article, but for the rest of the series, you should be familiar with PHP.
The Zend Framework
A couple of years ago, PHP sat at the top of the powerful-but-easy-to-use
scripting languages heap — at least as far as popularity was
concerned. It was installed on most UNIX®- and Linux®-based Web
servers. And if you were a programmer, it was easy to get a hosting account
that would let you use it. Ruby had been around for quite some time, but
not many people were using it. If you wanted to build a Web site using
dynamically generated content, but you weren't sure that you needed to go
so far as to use an application server like J2EE, you would very likely use
PHP. It was fast, easy to learn, convenient, and you didn't have to learn Perl.
And then — suddenly, it seemed — the landscape
changed. Ruby on Rails hit the programming world like a truck.
Object-oriented and based on the Model-View-Controller (MVC) paradigm, Ruby
on Rails presented a way to do what we all want to do: create a Web site
with virtually no effort. Of course, there were still two problems. For one
thing, you had to learn a new programming language. That's not a trivial
task, no matter what the language. And for another thing, if you found a
host that would let you run Ruby on Rails, you were very lucky. Most
wouldn't. If you've had the same account for a decade (as I have), you
might be a little slow to switch just because they don't have a new
programming language. Then, of course, there was the issue of all of the
existing PHP code you've written over the years. Did you really want a
ditch it all and start over? Of course not!
What is an enterprising PHP programmer to do? Create a new framework that
incorporates many of these new advantages, that's what. And, thus, the Zend Framework was born.
The Zend Framework provides clean, stable code, complete with
— and perhaps most importantly — clean
intellectual property rights. PHP is gaining ground in the enterprise
space, but if you're a Fortune 500 company, you don't want to take a chance
on a module submitted to a repository that may or may not be some other
company's intellectual property.
What is the Zend Framework, exactly? The Zend Framework:
- Is based on PHP
- Is object-oriented
- Uses the MVC paradigm
- Has open source contributors
- Has contributors who take responsibility for the fact that their code is not the intellectual property of someone else
It also aims to make your programming life easier, not just in general, by
instituting the MVC pattern, but also for specific things you tend to do
all the time, like access databases or output to a PDF file. (OK
— you probably don't output to a PDF file all the time. But I'll bet you would if it were easier.)
Zend Framework components include:
-
Zend_Controller
- This module provides the overall control for the application. It
translates requests into specific actions and makes sure they get executed.
-
Zend_Db
- This is based on PHP Data Objects (PDO) and provides access to databases in a generic way.
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Zend_Feed
- This makes it easy to consume RSS and Atom feeds.
-
Zend_Filter
- This provides string-filtering functions, such as
isEmail() and getAlpha().
-
Zend_InputFilter
- To
Zend_Filter, this is designed to work with arrays such as form inputs.
-
Zend_HttpClient
- This enables you perform HTTP requests easily.
-
Zend_Json
- This enables you to easily translate PHP objects into JavaScript Object Notation, and vice-versa.
-
Zend_Log
- This provides general-purpose logging functionality.
-
Zend_Mail
- This enables you to send text and multipart MIME e-mail.
-
Zend_Mime
- This is used by
Zend_Mail to help decode MIME messages.
-
Zend_Pdf
- This enables you to create new PDF documents, and load and edit existing PDF documents.
-
Zend_Search
- This enables you to perform sophisticated searches on your own text.
For example, you can build a search engine that returns results based on relevancy or other factors.
-
Zend_Service_Amazon, Zend_Service_Flickr, and Zend_Service_Yahoo
- These provide easy access to these Web service APIs.
-
Zend_View
- This handles the "view" portion of the MVC pattern.
-
Zend_XmlRpc
- This enables you to easily create an XML-RPC client. (Server capabilities are planned for the future.)
Now let's take a look at where we're going and what we're going to do.
The project
To show all of the ins and outs of the Zend Framework, we need a project
that covers a lot of ground. That's fine because my favorite project is
still the online feed reader. Why? Because I still haven't found one that
actually does what I want. Every time a new technology comes my way, I try
to make one that's better than the ones I've used before. So we're going to
create a new online RSS/Atom feed-reader service.
Does the world really need another online feed reader? Maybe. But I don't
care if I'm the only one who uses it. And that's the whole point: The Zend
Framework aims to make things simple enough that I can take on projects
just because I want to, and not because I've justified it with hundreds of
thousands of dollars worth of research. So what should this wonder of
news-mastering goodness do? For now, it should:
- Enable users to save sets of feeds or subscriptions
- Enable users to read feeds and individual items
- Enable users to save individual posts
- Enable users to search saved entries for particular text
- Enable users to easily read pages that don't have an RSS feed
- Enable users to print collections of postings
Over the course of this series, we're going to show you how to do all of
that using the Zend Framework. The series will run as follows:
-
Part 1: The basics
- This article, which explains the project in general and the Zend Framework.
-
Part 2: Adding a database
- This tutorial shows how to use the
Zend_DB
module to create and manipulate the central database used to store
subscription information, as well as saved entries and other information.
-
Part 3: The feeds
- Now we add feeds into the equation, enabling the user to create an
account, subscribe to particular feeds, and display those feeds. This tutorial uses the
Zend_Feed and Zend_Inputfilter modules, the latter used to verify e-mail addresses and to strip HTML tags from feed entries.
-
Part
4: When there is no feed: the
Zend_HTTPClient
- Not all sites have feeds, but it's still useful to track everything in
one place. This article shows how to use the
Zend_HTTPClient module to create a proxy to pull data into the feed-reader interface.
-
Part 5: Creating PDF files
- This tutorial explains how to use the
Zend_PDF module to enable the user to create a customized PDF of saved articles, images, and search results.
-
Part 6: Sending e-mail
- This article explains how to use the
Zend_Mail module to alert users to new posts and subscribed feeds,
and even to send those posts using HTML e-mail.
-
Part 7: Searching
- This article explains how to use the
Zend_Search module to search existing current and saved blog entries
for a particular search term and return ranked results.
-
Part 8: Adding related information and services
- This tutorial explains how to use the
Zend_Service modules to pull in information from other services
— specifically, Amazon, Flickr, and Yahoo! The interface
will use Ajax to pull books, photos, and search results related to a current blog entry or from a search term the user clicks.
-
Part 9: Adding Ajax
- The Zend Framework makes it easy to add Asynchronous JavaScript + XML
(Ajax) interactions to your application by automatically translating
native PHP objects to and from JavaScript Object Notation (JSON). This
article shows how to add this functionality to the feed reader. It also includes a basic description of JSON.
Setting up
The Zend Framework doesn't require any particular installation, but you
need to keep some requirements in mind. The Zend Framework requires PHP V5.
It is compatible with V5.0.4 and above, so you can use V5.1, but you don't
have to. You must, however, make sure that the library directory, where the
framework expects to find all of its files, is included in the include_path. To do that, be sure to set it in the php.ini file, as in:
; Windows: "\path1;\path2"
include_path = ".;c:\php\includes;e:\sw\zendframework\library"
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That's it.
The MVC pattern
When it comes to graphic design, I cannot draw my way out of a wet paper
bag with lighted exit signs. It's just not something I do well. However,
give me a design to put together by somebody with talent, and I can make
that interface do anything you want. So it's very helpful to be able to
break out the work involved in designing a Web-based application so
designers can do what they do well, coders can do what they do well, and
DBAs can do what they do well. That is the essence of the MVC pattern, which breaks a project down into three tiers.
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Defining Model-View-Controller
Patterns are, by definition, ways of doing things that have evolved
over years because they're a good solution to a problem. The
Model-View-Controller (MVC) pattern is no exception. Because of this
other organic means of creation, you will occasionally find differences
in definitions. For example, some definitions of the MVC pattern define
the controller's role as simply to change state, with all of the
business logic in the model tier. In the end, the only thing that's
important is that the application does what you want it to do most efficiently.
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The model tier consists of the representation of the actual data.
For example, in our feed-reader project, we have users, feeds, and feed
entries. Their representation in the database conceptually "models" their structure and, thus, consists of the model tier.
The view tier consists of the logic that actually defines how the displayed data looks. It doesn't decide what the displayed data is — just how it looks. In an ideal world, this template contains no logic. It simply takes the information it's given and displays it.
The controller is what actually defines what the data is. The
controller, in fact, is where all of the logic resides. In the Zend
Framework, this tier controls the actions to be executed. For example, if I want to display a single feed-item object, the responsibility is parsed like this: The feed-item object has a controller, which defines what happens when the display action is called. That action calls back to get the desired data from the model (in other words, the database or other persistent store), then feeds those fields — such as title, content, permalink, and so on — to the view, which simply displays it in the browser.
Granted, this is a departure for most PHP programmers. PHP has always been
a procedural language, despite the presence of objects. Nevertheless, the
trade-offs are definitely worth it. Building to the MVC pattern is much
easier than building an application in which everything is mashed together.
Now let's look at what's expected of you.
Coding guidelines
When you are coding for the Zend Framework, or even with the Zend
Framework, it is expected that you will follow certain guidelines. These
are designed to make group projects easier. In other words, by defining
coding conventions, you will not only avoid problems later but you will
also make it easier for others to read your code. The Zend Framework
documentation includes several pages of guidelines, including:
- Make sure the files are clean. In other words, no leading or trailing
spaces that can call a Web server to unexpectedly send content before
headers, standard indents of four spaces, etc.
- Start your class name with
Zend_ if and
only if it is intended to be part of the Zend Framework itself, rather than just an application that uses the framework.
- Underscores are forbidden in function names. Use camel-style lowercase
(as in
getTodaysDate()), instead.
- Start your variable names with an underscore only if they are private or protected.
- Declare all variables as private, protected, or public. Don't use
var.
- Use the standard PHP tag, as in
<?php ?>
— not the short form (<? ?>).
- Make sure your code is easy to read. In other words, when you use a
period (
.) to concatenate text, be sure to
put spaces before and after the period to make it more readable. The
same holds for adding spaces after commas when declaring an array.
- If you must pass-by reference, do it only in the declaration of a
function. Call-time pass-by reference is prohibited.
- Every PHP file must include documentation that can be read by
PhpDocumentor, and the coding guidelines specify certain minimum tags.
This is not a complete list of guidelines, of course, but it should give
you an idea of the types of requirements. Check the documentation for the
full list, so your code more easily fulfills the promise of making PHP projects easier to share.
Summary
The Zend Framework provides a new IP-certain way to build your PHP
applications. In that, it aims to improve your PHP coding experience. In
this series, we use the Zend Framework to build an RSS/Atom feed reader.
Future parts of the series will cover data access, searching, Web services,
and other portions of the framework. In Part 2, we
create the login system and start building the database.
Resources Learn
-
The Zend Framework Web site maintains the latest documentation, as
well as installation FAQs.
- Learn more about Zend Core for IBM, a seamless, easy-to-install, and supported PHP development and production environment that features integration with DB2 and Informix databases.
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To better understand the goals of the feed-reader project, read "Introduction to Syndication, (RSS) Really Simple Syndication," by Vincent Luria.
-
Thought Storms ModelViewController explains the MVC and the controversy and confusion surrounding it.
-
The phpPatterns Web site explains MVC from the PHP point of view.
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PHP.net is the central resource for PHP developers.
-
Check out the "Recommended PHP reading list."
-
Browse all the PHP content on developerWorks.
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Expand your PHP skills by checking out IBM developerWorks' PHP project resources.
-
To listen to interesting interviews and discussions for software developers, check out developerWorks podcasts.
-
Using a database with PHP? Check out the Zend Core for
IBM, a seamless, out-of-the-box, easy-to-install PHP development and production environment that supports IBM DB2 V9.
-
Stay current with developerWorks' Technical events and webcasts.
-
Check out upcoming conferences, trade shows, webcasts, and other Events around the world that are of interest to IBM open source developers.
-
Visit the developerWorks Open source zone for extensive how-to information, tools, and project updates to help you develop with open source technologies and use them with IBM's products.
-
Watch and learn about IBM and open source technologies and product functions with the no-cost developerWorks On demand demos.
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About the author | | | Nicholas Chase has been involved in Web-site development for companies such as Lucent Technologies, Sun Microsystems, Oracle, and the Tampa Bay Buccaneers. He has been a high school physics teacher, a low-level radioactive waste facility manager, an online science fiction magazine editor, a multimedia engineer, an Oracle instructor, and the chief technology officer of an interactive communications company. He is the author of several books, including XML Primer Plus (Sams). |
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