Problems editing php.ini in ssh and sudo

I am trying to edit my php.ini file via ssh on /etc/php54/php.ini, but when I try to save it, it says “permission denied”, even though I am logged in as sudo vps admin. What could be the issue?
Furthermore, Dreamhost support told me to paste this line in Terminal:

sudo su /etc/php54/php.ini

But when I do, it says:
Unknown id: /etc/php54/php.ini

I then tried:
sudo /etc/php54/php.ini

But then I get the error:
sudo: /etc/php54/php.ini: command not found