After upgrading to Ubuntu 18.04 LTS, I encountered this issue with arc: “PHP CONFIGURATION ERROR”. Here it is a really quick fix.

How to fix “PHP CONFIGURATION ERROR”

I started using arc (also know as Arcanist, a Phabricator tool for CVS workflow) with Ubuntu 17.10 on a Dell XPS 13.

A week ago, I upgraded my system to the shiny Ubuntu 18.04 LTS. It went all fine, except for arc that started throwing this error when executed:

$ arc

PHP CONFIGURATION ERRORS

You need to install the cURL PHP extension, with 'apt-get install php-curl'.

The strange thing is that the recommended fix was not working at all.
I didn’t investigate (I wanted to come back operative as fast as possible), but I highly suspect that it was probably related to the new PHP version.

However, to fix the error I just reinstalled php-cli with:

sudo apt install php-cli

If this does not work, try also:

sudo apt install php7.2 php7.2-common php7.2-cli