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.
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.
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