Features reviewed

The following are the main PHP V5.3 features I look at in this article:

• Late static binding
• Namespaces
• Class method overloading
• Variable parsing and heredoc

However, before digging in, you need to set up PHP V5.3.

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Setup

PHP has a reputation for being a bit difficult to set up. This is probably because a PHP installation sits on a Web server (Apache, for example) and often has a connection to an external database (MySQL, for example). Also, in a sense, PHP script code sits inside HTML code. In other words, PHP as a technology straddles a number of complex areas and disciplines. So, before you write a single line of PHP script code, you have to jump through a lot of hoops. I wish I could change all that, but many things to do with software technology are still quite difficult.

However, for those lucky readers using Apple Macs, the setup is about as simple as anyone could hope for:

1. Get a copy of a PHP binary installer (http://www.entropy.ch/software/macosx/php/).
2. Switch off Web Sharing in System Preferences.
3. Locate the /etc/apache2/httpd.conf file.
4. Comment out the following line in the httpd.conf file: LoadModule php5_module.
5. Run the PHP V5.3 installer (you can build the source code if you prefer).
6. Switch on Web Sharing in System Preferences.

I don't want this article to be just about installation, so if your platform is Microsoft® Windows® or Linux®, have a look at one of the many excellent PHP reference books available (see Resources for my recommendation).

To check that PHP is installed and that you're running the correct version, create a file called phpinfo1.php in the /Library/WebServer/Documents folder. Listing 1 illustrates the contents of the required script file. All the scripts in this article are available as part of the compressed (ZIP) file in the Download section, so you don't actually have to create any files if you want to follow along.

<?php
phpinfo();
?>

After you place the script file in the /Library/WebServer/Documents folder, go to http://localhost/phpinfo1.php. You should see something like the excerpt illustrated in Figure 1. You might have to replace the word "localhost" in the URL with the IP address of your host machine.

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Late static binding

PHP V5.3 extends the use of the static keyword. Static class methods and properties are accessible without the need for an instantiation of the class. This can be convenient for those situations where an object of the class is not available or not desirable. Listing 2 illustrates an example of late static binding.

<?php
class A {
    public static function who() {
        echo 'Calling who method from class '.__CLASS__;
    }
    public static function test() {
        static::who();
    }
}

class B extends A {
    public static function who() {
         echo 'Calling who method from class '.__CLASS__;
    }
}

B::test();
?>

The code in Listing 2 produces the following output:

Calling who method from class B

Prior to PHP V5.3.0, the method in class A might have been defined as self::who(). Unfortunately, this would have resulted in an invocation of the function from class A, rather than the one in the subclass class B. The use of the static:: keyword in PHP V5.3.0 fixes this by allowing you to reference at runtime the class method that was initially invoked. The latter is obviously the intention of the code in Listing 2.

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Namespaces

PHP V5.3 provides namespaces to enhance the encapsulation strength of the language. Namespaces are quite common in modern languages, such as C# and XML. The main merit of namespaces is that they allow you to define isolated containers for code symbols (classes, functions, and constants), which sounds more difficult than it is. Listing 3 shows an example of using PHP namespaces to define local and global string constants.

<?php
namespace test;
define('ASTRING', 'Hello World!');
define('test\ASTRING', 'Hello World from my namespace!');

echo "<p>My string is: ";
echo ASTRING;
echo "</p>";

echo "<p>My string is ";
echo \ASTRING;
echo "</p>";
?>

The code in Listing 3 produces the following output:

My string is: Hello World from my namespace!
My string is: Hello World!

So, what's going on in this code? Well, the first define statement creates a string constant called ASTRING in the test namespace. When you then refer to the ASTRING string, the engine looks first in the local test namespace. This is why you see the locally defined string appearing first. Then, when you want to see the globally defined string, you simply use the syntax \ASTRING. These simple rules allow you to dip into any number of namespaces with no need to worry about name collisions.

The namespace facility allows for clearer code-level separation than before. This, in turn, helps to facilitate code integration in team environments. In other words, different teams can allocate their own namespaces and, when that convention is respected by all team members, the number of name clashes should be reduced to zero. This is, again, an object-oriented type of improvement in the PHP language that comes with V5.3.0.

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Class method overloading

The term overloading in PHP is a little different from the usual object-oriented context. In the Java™ language or C#, an "overloaded" method is one that provides code for a range of different parameter lists. For example, if I have a method called draw(String str), an overloaded version can have the following form: draw(String str, int i). This use of the method symbol name is referred to as the method signature and, for the purposes of overloading, the return type is ignored.

In PHP, "overloading" is used to refer to dynamically created methods and properties. This is in effect dynamic code, and any such dynamic entities are processed by what are called magic methods. You can create these magic methods in a class for a variety of action types. Then, the overloading methods are invoked at the point in your code where you interact with undeclared or invisible properties or methods. This style of language overloading provides you with a substantial degree of flexibility.

This all sounds complicated, so look at an example to make it more concrete. Listing 4 illustrates using PHP overloading to invoke object and class methods.

<?php
class OverloadedMethodTest {
    public function __call($name, $arguments) {
        // The value of $name is case sensitive.
        echo "Calling object method '$name' "
             . implode(', ', $arguments). "\n";
    }

    /**  As of PHP 5.3.0  */
    public static function __callStatic($name, $arguments) {
        // The value of $name is case sensitive.
        echo "Calling static method '$name' "
             . implode(', ', $arguments). "\n";
    }
}

$obj = new OverloadedMethodTest;
$obj->runOverloadedTest('in an object context');

OverloadedMethodTest::runOverloadedTest('in a static context');  // As of PHP 5.3.0
?>

The code in Listing 4 produces the following output:

Calling object method 'runOverloadedTest' in an object context
Calling static method 'runOverloadedTest' in a static context

Notice in Listing 4 the way the overloaded code has inferred the method names and parameters from the invocation code as follows:

$obj->runOverloadedTest('in an object context');

OverloadedMethodTest::runOverloadedTest('in a static context');  // As of PHP 5.3.0

This type of power does require a large degree of responsibility on the part of the programmer. The overloading facility provides for flexible code, but it also provides fertile ground for errors. So, overloading should be used with caution, along with a strong code-testing discipline.

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Variable parsing and heredoc

One of the great strengths of PHP is string parsing. PHP has no limit on the size of a string, aside from the amount of host memory available. Listing 5 shows an example of the flexibility you get when using PHP parsing.

<?php
$beverage = 'coffee';
// The following works; "'" is an invalid 
character for variable names
echo "$beverage's taste is great";
// The following won't work; 's' is a valid 
character for variable names but the 
echo "He drank a number of $beverages";
variable is "$beverage"
echo "He drank some ${beverage}s"; // works
echo "He drank some {$beverage}s"; // works
?>

The code in Listing 5 produces the following output:

coffee's taste is great
He drank a number of 
He drank some coffees
He drank some coffees

The code in Listing 5 isn't new to PHP V5.3.0. It is included simply to remind you about the string handling support and some of the parsing rules. However, PHP V5.3.0 adds enhanced heredoc syntax support. Listing 6 shows a simple example.

<?php
echo >>>"FOOBAR"
Hello World!
FOOBAR;
?>

The code in Listing 6 produces the following spectacular output:

Hello World!

So, what's special about Listing 6? Well, the heredoc support in PHP V5.3.0 allows the use of double quotes. What benefit does this provide? Mainly, that the content inside the double quotes is not parsed, which provides you with more flexibility. Basically, this just adds a little more flexibility to the already-strong string support. The online references for PHP V5.3.0 include lots more material about this and other topics related to PHP V5.3.0.

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Conclusion

PHP is an attractive technology. It facilitates a pick-and-mix model of Web-site development. You can add a database to your Web site and the PHP language has bindings necessary to achieve this with ease. You don't need heavyweight application servers or servlet technology. In other words, you get to control the environment with a minimum of investment — both financial and intellectual.

The PHP language continues to evolve, and I'm glad to see that many V5.3.0 improvements are effectively enhancements to the object-oriented aspects. This helps PHP compete with the more heavyweight (and more expensive) approaches to Web design.

In this article, I looked at late static binding, namespace support, class method overloading, and heredoc support. This is only a tiny part of the world of PHP V5.3.0. There are many other topics, such as migration to V5.3.0. Check out the Resources section for details on these and other areas.

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Download

Information about download methods

Resources

Learn

• PHP and MySQL Web Development, by Luke Welling and Laura Thompson, is an excellent PHP reference book.
  
  
• Read "Create better namespaces in PHP" to learn more about using namespaces in PHP.
  
  
• "PHP object orientation: Separating concerns" discusses object-oriented design with PHP.
  
  
• PHP.net is the central resource for PHP developers.
  
  
• Check out the "Recommended PHP reading list."
  
  
• Browse all the PHP content on developerWorks.
  
  
• Follow developerWorks on Twitter.
  
  
• 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, as well as our most popular articles and tutorials.
  
  
• Watch and learn about IBM and open source technologies and product functions with the no-cost developerWorks On demand demos.
  
  

Get products and technologies

• Learn more about PHP V5.3.0.
  
  
• Innovate your next open source development project with IBM trial software, available for download or on DVD.
  
  
• Download IBM product evaluation versions or explore the online trials in the IBM SOA Sandbox and get your hands on application development tools and middleware products from DB2®, Lotus®, Rational®, Tivoli®, and WebSphere®.
  
  

Discuss

• Participate in developerWorks blogs and get involved in the developerWorks community.
  
  
• Participate in the developerWorks PHP Forum: Developing PHP applications with IBM Information Management products (DB2, IDS).
  
  

About the author

Comments (Undergoing maintenance)

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Table of contents

• Features reviewed
• Setup
• Late static binding
• Namespaces
• Class method overloading
• Variable parsing and heredoc
• Conclusion
• Download
• Resources
• About the author
• Comments

Next steps from IBM

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• Tutorial: In this Mastering Facebook app development tutorial series, you will use Java and PHP in parallel to build a Facebook interface for an online stock trading J2EE application using the Spring framework.
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