php - chmod issue with particular user

I'm starting with chmod. I've set up a group and gave them permission (777) and every user inside the group is able to do whatever they want inside the directory /www/.

However, I need to change the permissions to anyone else. So I wrote down:

$ chmod -R o-rwx /www/ && chmod -R o+rw /www/some_interesting_dir

Because I wanted only to allow him access to that directory. But he's unable to perform "cd /www/some_interesting_dir", console says permission denied.

What am I doing wrong?

Thank you very much!