Perl
Perl is not only a Web-scripting language, and looking at is as such only shows a microcosm of its true nature. Perl is, at its most basic level, a text-manipulation language. It provides powerful features that allow the user to easily do some operations that are very complex in C, and also complicates some other things that are easy in C! Perl, in conjunction with CPAN (the Comprehensive Perl Archive Network) offer an enormous amount of "ready-made" modules, that allow code to be reused and shared- database interface modules, CORBA modules, scientific calculation modules, network programming modules, SGML/XML/HTML modules, and so much more. Obviously, because of Perl's powerful and easy text manipulation functions, it was quite natural for web developers to expand their toolbelt to include Perl. Perl can be embedded within HTML documents, run as an SSI (Server-Side Include), or run as its own application (CGI, or Common Gateway Interface). Perl, as applied to CGI and web application design, is designed for the programmer who wants to "output" webpages. A Perl Web application is nothing more or less than a backend program, that interacts with the browser using HTML.
PHP
PHP is an embedded scripting language. A PHP-aware webserver parses HTML documents looking for PHP code, processes it, and sends the results back to the browser. PHP's popularity lies in the fact that it is easy to use, and is readily embeddable into HTML documents. Using PHP in conjunction with your favorite HTML editor is an increasingly popular way to provide dynamic web content, with minimal programming. In effect, PHP separates web design from application design. I've worked on a couple large PHP projects where the HTML designers were not even part of the application design team. PHP is developed with the web, and web development in mind.
PHP seems very much in vogue now - with most web hosts providing support for it. For those who have only vaguely heard of it and are not too sure what it is, this article discusses PHP and informally compares writing PHP scripts with writing CGI scripts in Perl.
PHP is a free server side scripting language. It can be built into web servers like Apache and you can use it to generate your pages dynamically. You will probably use it in situations you would have otherwise used a Perl CGI script for. For example, the PHP feedback form generated by thesitewizard.com's Feedback Form can be used by visitors to your website to send feedback to you.
