CGI (the common gateway interfaces) allows a server-based script to get access to form fields submitted by a user. Such scripts can be written in Perl, PHP, VBscript as well as other scripting languages.
Assume you must create a script to "echo" (display) back to a Web page the values a user has entered into your form. Which language would you select and why?
(this is a question in a design class I am taking)
dunno if this is a "trick question", but given the trivial nature of the problem given, any language would be suitable.
As for performance, the overhead of using CGI (who uses CGI any more?) far outstrips any interpreter speed issue. Anybody citing that they will use "x" because "x" is faster gets a big red X on their answer...
Use whatever language is (a) available and already installed on your host and (b) you are familiar with.
The why - the problem is trivial, performance doesn't matter - language elegance doesn't matter (because it's probably a one-line solution in most - and if it isn't, pick another one...) - the right answer is to use the tool that will allow you to get the job done most quickly.