PHP pages

[#1]

Hi
I want to run a small php script on the website I am building for myself to send create and send an email with the use of a form. It is essentially the same form I have used on many PHP enabled sites through otherhosting providers in the past with no problem at all.
Unless I am wrong I have PHP enabled on my domain (craigomatic.co.uk) but when a page is accessed it reacts as if it isn't. ie. it downloads the page as a file.
What have I missed?
Craig

[#2]

OK. A quick update.
I have discovered that I need to use cshell.plus.net rather than ftp.plus.net to upload my files, but I can't work out where they should be uploaded to (inside or outside the cgi-bin folder) and when I have, what will the url be of the uploaded file.
Ideally I'd like to have a url along the lines of http://www.mydomain.co.uk/index.php

[#3]

The script will be called using http://ccgi.mydomain.co.uk/directory/scriptname
You will need to add the appropriate DNS records from https://portal.plus.net/my.html?action=domainv2&?membermenu=domainnames

[#4]

Thanks Jelv
I've managed the first part. Uploaded files and can view the by the ccgi.mydomain etc address, and hopefully on this occasion that is all I need for what I want to achieve. I think.
But I'm a bit confused about updating the DNS settings, and for future reference I probably should know these things if I want to grow the site a little.
I'm assuming that you are suggesting that  to have a sensible address such as www.mydomain.co.uk/index.php, I need to point the domain at the CGI  server rather than the standard server, but I'm no expert on the matter and the instructions don't seem clear to me about what I need to add or change. Obviously its not the MX records.

[#5]

If you've got ccgi.mydomain etc working then there's nothing to do with the DNS. It would be necessary if you had added the domain after you activated CGI.
You can move your whole website across to ccgi (eg. if it is all php such as a content management system) and get www pointed to the ccgi server; however there's no problem with having a ccgi based script embedded in www pages hosted on the normal homepages server (I've done that for years).

[#6]

Yup, it could potentially cause issues with cross-domain scripting, say a javascript under www subdomain needed  to access something from a page served from ccgi subdomain, like ajax applications, but for most purposes no problem.
If you did need to point your domain at the ccgi server, here are a couple of recent threads on that: thread, thread.
Gabe