Hmmm... I dont know that this is possible in PHP. It would be very difficult to do at any rate. What you are talking about is having a person log in (I assume), then say there stuff is at ftp://ftp.blah.com:21/mysite/
then you would have to make a socket connection:
$fp = fsockopen("ftp.blah.com",21);
then read the directory
fputs($fp,"$user");
fputs($fp,"$passowrd");
fputs($fp,"cd $site");
fputs($fp,"ls $site");
$files = $fgets($fp,10000);
this would return the files on the server. Then you would have to use this and:
then I guess you could close the socket... (since you have a list off all the files), I guess you could fopen(); each file since its their webpage and its all available over the net and write it to there directory. But then you would have to worry about, permissions, and .... ugh, man this would get messy. This is the only way I think this could possible be done. But do you really want to create that much of a load on your server, through a webpage? And what about time out... you would have to worry about that as well. If you were really really clever you could right a C program or something. That the PHP script would start, then the user would wait for say 15 min (max) while his site transfers. But going through the webserver is just messy. Who knows though I could be completely off my rocker. 🙂
Hope this Helps!
(PS. I have tested none of that code)