By Tobias Ratschiller, Intranet Design Magazine
1. Introduction to PHP
What have sprint.ca, livebid.amazon.com, xoom.com, and
mp3.lycos.com in common? All employ one of the Web’s hottest server
side technologies: PHP, the PHP Hypertext Preprocessor.
While the success of Open Source software like Linux or Apache
has been documented extensively throughout all mainstream media,
the rise of PHP has gone largely unnoticed. Still, the Web
scripting language PHP is the most popular module for the Apache
Web server, according to a E-Soft survey (http://www.e-softinc.com/survey/).
Netcraft studies have found that PHP is in use on over 6% of all
Web domains in the world (see http://www.netcraft.com/survey).
That is an incredible market penetration for a rather specialized
product. This popularity continues to rise exponentially, with the
new version 4.0 just around the corner. Increasingly, this is being
reflected in traditional media: By May 2000, more than 20 books
about PHP have been published in different languages, with more in
the pipeline. Commercial players are beginning to join the
bandwagon: PHP is included with Web servers, for example C2’s
Stronghold, and Linux distributions. A new company, Zend
Technologies, has been formed to provide commercial add-ons and
support for PHP. A long list of large-scale Web sites employ PHP,
as well as hundreds of thousands small to medium Web sites. Enough
reasons to take a closer look at PHP.
What Is PHP
PHP is a programming language, used on the server to create dynamic
Web pages. The principles of this technology are similar to
Allaire’s ColdFusion, Mod_Perl, Sun’s JSP, or Microsoft’s ASP,
which all address one problem: As Web sites and intranets get
larger and more complex, static HTML files hit their limits. Today,
the Web is an interactive, transaction-oriented business platform,
featuring advanced Web-based applications such as online commerce,
business information systems, and collaborative computing
environments. To develop such applications, you need a technology
to generate dynamic content for Web pages.
Traditionally, developers have used CGI (Common Gateway
Interface) scripts for interaction with users, querying databases,
and so forth. However, because CGI scripts are separate software
programs, which get executed as stand-alone processes whenever a
user requests the script, scalability was lacking – CGI scripts
could quickly consume all available memory and CPU power. Enter
PHP: Rasmus Lerdorf, a then Toronto-based IT-consultant, developed
it in late 1994 as a quick hack to embed macros into HTML pages, to
avoid the forking of external programs. When he decided to make his
project open source, it proved to be popular, and users started to
contribute to it. In 1997, Zeev Suraski and Andi Gutmans, two
developers from Israel, rewrote the core engine of PHP, the
language parser, and made a complete programming language out of a
pet project. The current rewrite, PHP 4.0, is again much cleaner,
especially with complex scripts and when used in business
environments.
Architecture Overview
Working with PHP leads to a three-tier architecture in such a
coherent way that many developers don’t even notice it. In the
first tier there is a thin client – translated to the world of Web
applications, this would be the browser. The middle tier
(application server) is obviously PHP and the Web server as host
application, while the third tier consists of a database
system.
PHP scripts are often embedded in the HTML code of page, and
then get parsed on the server-side – the browser sees plain HTML
only. A typical Hello-World script looks like this:
<html>
<? print("Hello World!");?>
</html>
This is the method that novice developers find the easiest to work
with. Larger and more complex applications usually go other routes,
to enforce a cleaner separation of layout and application logic.
When embedding the script directly in HTML, average, HTML-literate
Web designers cannot easily edit the contents of the page without
being familiar with the scripting language used. PHP offers a
variety of libraries to work with page templates, which solve this
problem, and introduce an efficient development methodology and
simplify maintenance. This way, developers focus on the application
logic, and designers can change the layout of a dynamic page
without involving the developer or interfering with the program
logic. This translates into faster application development, and
makes maintenance tasks easier by dividing them into content and
logic tasks, which can be handled by separate team members.
PHP needs not be used for Web development exclusively. It can
also be compiled as stand-alone script interpreter, and handles
simple system administration tasks as well. For example, you could
use a small PHP script to send daily statistics from your
e-commerce application. In version 4.0, the language core engine,
the Zend parser, has been abstracted enough to be embeddable in
other technologies. Rumors go that is planned to integrate PHP as
stored procedure language into the popular MySQL database system.
Seeing the dynamic evolution of PHP, it is only logical to expect
the language to grow into other scenarios – why not use PHP as a
macro processor in a word processor?
New Challenges
As you’ve seen, the new opportunities created by the Web bring new
challenges to IT organizations building the applications. Choosing
the right technology is critical to the success of any Web
application development project. The main challenges are an
increased demand on productivity, connectivity, portability, and
performance.
2. PHP Meets Development Challenges
The first advantage of PHP was one common to many Open Source
projects: It simply delivered, while other technologies were still
vapor ware. PHP pre-dates ASP, Mod_Perl, and ColdFusion by at least
12 months. Over the years, PHP had the opportunity to strengthen
its core base and to integrate more features, and provides today a
base that can easily stand out in the increasingly crowded
server-side application development platform market, as the
following points will show.
Faster Time to Market
The development time of Web applications is measured in days and
weeks – dinosaur projects spanning multiple years belong to an era
which many Web developers don’t even remember. IT managers and
developers are struggling to keep up with this pressure, and demand
high productivity from their development environments.
Perl is a general scripting language, Java is a full-fledged,
complex programming language, Visual Basic Script and JSscript have
been post-integrated into ASP – PHP, on the other hand, was built
with the needs of Web developers in mind. In Web application
development, there is no itch you can’t scratch with PHP. Unlike
other cumbersome, overhead-laden approaches, PHP is lightweight and
focused on the Web – where it can solve complex problem scenarios
quicker and more easily than comparable technologies.
The syntax and grammatical structure of PHP resembles the C
programming language with the complexity (for example, memory
management, pointers, and strong typing) taken out. The developers
of PHP aren’t hesitant to integrate the best features of other
languages, though, so you’ll find elements of Perl and Java in PHP
as well. For programmers familiar with C, Perl, or Java, it is a
matter of days to get acquainted with PHP. Thanks to the excellent
reference manual, anyone of your developers can probably produce
small database enabled applications after just one afternoon.
Abundant Connectivity
And there’s a lot to explore. For example, PHP implements native
interface to a wide variety of database engines, from Open Source
systems like MySQL or PostgreSQL to commercial products like
Oracle, SQL Server, DB2, and many more. The native database access
offers better performance and tighter control than layered access
methods such as ODBC (which is still available for databases not
supported natively). Especially on the Web, a fast response time is
crucial for the success of applications.
Besides databases, PHP supports most current Internet standards:
IMAP, FTP, POP, XML, WDDX, LDAP, NIS, and SNMP – to list only a few
of the acronyms which will inevitably get a twinkle into your
developers eyes. For corporate and IT needs, this simply means that
PHP is able to talk to different standards and technologies with
ease: All from one common tool set, without the need for expensive
third party modules.
Leveraging Enterprise Logic
I hear you say already: “Nice features – but unfortunately, we’ve
all of our business logic already developed with Foo”, where Foo
stands for Java classes, Enterprise Java Beans, or COM components,
depending on your corporate bias. Indeed, others have had these
thoughts, and since version 4.0, PHP supports direct access to Java
objects on any system with a Java Virtual Machine available, as
well as Distributed COM on Windows. Multiple Web applications can
reuse the same components. This enables you to keep your business
logic in separate components, and use PHP for what it does best,
and where it outperforms its alternatives: Web application
development. This means a significantly lower Cost of Ownership: It
enables business to leverage existing technology and develop new
applications in an easier way.
Portability
When mentioning Java, one if its key features comes to mind
instantly: portability. Up until version 3.0, PHP could be
integrated only as module into the Apache Web server, or run as
separate CGI program, which would eliminate many of PHP’s speed
benefits. In version 4.0, however, the Web server interface (Server
API, or SAPI) has been abstracted, and PHP now integrates well with
different Web servers: iPlanet/Netscape Enterprise Server, IIS,
Apache, Zeus, fhttpd, and so forth. Platform independence has
always been an advantage of PHP: It runs on all popular Unix
platforms, including Linux, on Windows, on MacOS, and even on
OS/2.
Portability is the key to scalable applications. You can run the
same application on a low-scale Linux box and on a high-end Solaris
machine, without the need to worry about platform-specific
features. Also, PHP interfaces transparently with clustering
solutions from simple Round Robin IP clusters to advanced Cisco
solutions.
The broad platform support can be directly attributed to the
fact that PHP is distributed with full source code. Anyone with the
necessary skills can port PHP to a new operating system. The
resulting modifications to the core system can then be contributed
back to the community.
Open Source
Open Source software in general means a number of significant
advantages for the corporate IT infrastructure. Because the full
source code is available, it can be inspected in thorough security
audits. If third parties find security issues, they’re usually
fixed within hours or days. If no one is going to do it, you can
assign your own personnel to it – with the full code in your hands,
you’re no longer dependent on external software manufacturers.
Then there’s the community. Free help is available from mailing
lists, newsgroups, and IRC channels. The PHP core developers
participate in these support forums, and provide developers with
top-level advice – usually within hours. I’m certain that more,
commercial support options will be available in a very short
time.
Open Source brings with it that rough edges are corrected
promptly, and that the overall strategy is un-bureaucratically
adjusted to new requirements. For example, originally no one had
thought that PHP would be used in most sophisticated business
scenarios, and only version 4.0 is really prepared for this
environment.
Performance
Therefore, while the speed of PHP 3.0 was sufficient for the
average, medium-sized Web application, scalability for advanced
applications could be a problem. The plain, out-of-the-box 4.0
version is already multiple times faster than PHP 3.0, introducing
a performance boost, which will make some clustering systems
superfluous. Plus, there’s the Zend Optimizer, a free add-on module
from Zend Technologies. It performs on-the-fly code optimizations
to enhance the running speed of PHP applications. An application
that uses the Zend Optimizer, typically executes 40% to 100% faster
than one without.
Pointers
Official PHP Homepage: http://www.php.net
Zend Homepage: http://www.zend.com
Conclusion
Considering the vastly growing amount of servers on which PHP is
now running, taking a look at the huge step PHP made from version
3.0 to version 4.0, and seeing its mature and up-to-date base, PHP
has surely become what it has been aiming at: A great tool for
rapid development of stable and fast Web applications. If your
business relies on Web applications, you should certainly consider
PHP. Gone are the days, when a business could post static pages on
a Web site – today, sophisticated Web applications demand that
companies use technologies that can provide them with rapid
development, performance, scalability, openness, and security – and
PHP is a strong option in the Web application development area.