What is it?
PHP is an HTML-embedded scripting language, used mainly for server-side scripting. The abbreviation originally stood for "Personal Home Page" but it is now recognised to be "PHP: Hypertext Processor".
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PHP is one of the Ps in the Lamp (Linux/Apache/MySQL) stack, with Perl and Python as alternatives.
From the outset its main purpose has been to enable developers to create dynamic web pages quickly. PHP is open source, free software, with a supportive community and a great deal of free training material.
After a year of moderate decline, PHP usage has resumed its growth, according to the monthly Netcraft survey of internet trends.
The Tiobe Community Programming Index currently places it fifth after Java, C and C++, and Visual Basic in terms of worldwide availability of skilled engineers, courses and third-party suppliers.
Evans Data Corporation suggests that in the US it is one of the languages ousting Visual Basic as the focus for development moves from the desktop to the web.
Where did it originate?
PHP was created in 1994 by Rasmus Lerdorf, who wanted to display his CV and track visits on his personal home page. On release in 1995, it also included Lerdorf's Forms Interpreter, and was called PHP/FI.
Zeev Suraski and Andi Gutmans created what became known as the Zend Engine, and later founded Zend Technologies, which maintains the language. PHP 5, with Zend Engine II, was released in 2004, adding greater support for object orientation, MySQL and Simple Object Access Protocol, among other enhancements. PHP 4 is still going strong.
What's it for?
According to Security Space's monthly internet reports, PHP is the most popular add-on module to the Apache web server, used by more than 40% of Apache sites.
By contrast, Perl is used at 9.5% of Apache sites and Python at just under 2%. As well as server-side scripting, PHP is used for command line scripting, and even for desktop applications.
What makes it special?
PHP's supporters claim it has C's elegant syntax and Perl's powerful performance, without the complexity of either.
How difficult is it to master?
You will need a working knowledge of HTML, and a background in C, Perl or Java is helpful, though for beginners it is easier than any of these.
Where is it used?
PHP users include Hewlett-Packard, Nortel Networks, Boeing, Lufthansa and Disney. It is shipped and supported along with most Linux distributions. It is also favoured by organisations with small budgets and no full-time IT staff.
What systems does it run on?
Every web server (but especially Apache) and most operating systems.
What's coming up?
PHP 6 is already in development, with a specification based on users' responses to PHP 5. Some gaps, such as native Unicode support, will be filled. The Zend Framework, a collection of building blocks and best practices, is being put together to make PHP more competitive with the likes of ASP.net.
Start with the following websites:
There are plenty of others, especially if you combine your search with other elements of the Lamp stack, such as MySQL. O'Reilly's ONLamp is a good source. For more formal training, and certification management see:
Rates of pay
Developers who combine PHP with other web skills can look for a salary of £30,000 and upwards.
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