Looks like php5-cli is in the ubuntu security repos, which doesn't appear to exist in your sources.list
Try adding this to your sources list, then apt-get update, apt-get install php5-cli or apt-get install php5
Code:
deb http://security.ubuntu.com/ubuntu hardy-security main
Ubuntu -- Details of package php5-cli in hardy
http://packages.ubuntu.com/hardy/i386/php5-cli/download