Do the following to make php sessions and file write work in Sourceforge hosting

sftp someuser,onlinepasswords@web.sourceforge.net

where
- someuser is the username and
- onlinepasswords is the project name

when you log in you will be at this directory /home/groups/o/on/onlinepasswords
in the persistent directory within this directory is where you can write files
This folder is used to write file based php sessions and other flat files

Create a directory sessions under persistent
Make sure you give 777 to this directory

Create a .htaccess file on the demo directory and add the below directive
php_value session.save_path 0;600;/home/groups/o/on/onlinepasswords/persistent/sessions

You php file based sessions will get saved here

Follow the same procedure as above for the most part

Create a directory “files” for example under persistent

chmod 777 files

Use the full path

/home/groups/o/on/onlinepasswords/persistent/files/somefile.txt and you will be all set

Now although you can use the below path it is not recommended:
/home/persistent/o/on/onlinepasswords/files/somefile.txt