creating files on a remote host

Is there a way to create a file to a remote host. IE: I have a php script on www.somedomain.com for example - and I want to fill out a form on this php script and make it create a file called "index.html" on say www.someotherdomain.com for example. I have admin and root access to BOTH domains. Is there a way I can popen or fopen a file using ftp username and password? The end result - I want to create index pages on the fly by filling out a form - which will in return create the page for my other web sites. So far, I have successfully created the index page. But to get it to the other site I am manually downloading the index page to my local computer, and uploading it to its new site - Not the most effective way to do things. Any ideas??? Thanks in advance Dave