PHP, which stands for "PHP: Hypertext Preprocessor", is an HTML-embedded scripting language. Much of its syntax is borrowed from C, Java and Perl with a couple of unique PHP-specific features thrown in. The goal of the language is to allow web developers to write dynamically generated pages quickly. The scripts are interpreted by the server, so it works with all browsers.
As a simple example:
<HTML>
<HEAD>
<TITLE>PHP Example</TITLE>
</HEAD>
<BODY>
This is standard <B>HTML</B>
<?
printf("This is PHP, the time is %s",date("g:ia"));
?>
</BODY>
</HTML>
Notice how this is different from a CGI script written in other languages like Perl or C -- instead of writing a program with lots of commands to output HTML, you write an HTML script with a some embedded code to do something (in this case, output some text). The PHP code is enclosed in special start and end tags that allow you to jump into and out of PHP mode. What distinguishes PHP from something like client-side Javascript is that the code is executed on the server. If you were to have a script similar to the above on your server, the client would receive the results of running that script, with no way of determining what the underlying code may be.
I have tried to make the minimum of changes whilst porting PHP, so it should behave very similar to any other platform. Thus a script written in RISC OS should behave the same when uploaded to a Unix web server, or vice versa.
PHP can be run on its own, and you only need a web browser to view the output, but it is most use as a CGI program for a web server. It has been tested with the Navaho server suite, Netplex, WebJames and the ANT server suite. It does not work with DeltaNet or WebServe.
Alternatively, you can download a version of WebJames that has a PHP handler built in. This is the fastest method.
There is more information about PHP in general at http://www.php.net/
If you want a free ISP that supports PHP, try UKLinux
Download version 2.23 6-May-07 (3003k)
Changes from previous versions
Source code patches for version 2.23 (1k)
and Ovation Pro format (980k) Thanks to Keith Hopper for doing the Ovation Pro conversion.