Error with cURL PHP extension when running arc

Can you show us the output of this command?

$ php -i

Here:

http://pastebin.com/MxZNvBeg

Okay, how about this?

$ php -r 'echo function_exists("curl_init") ? "YES\n" : "NO\n";'

It returns "YES"

How about this?

$ /usr/bin/env php -i

Huh, when I run that, it shows PHP Version => 7.1.0. Why would this be different? I even uninstalled php7 from my computer.

You have installed multiple versions of PHP, some of which have cURL and some of which do not.

This is a distribution / package management / system administration problem unique to your environment rather than a Phabricator issue, and thus far outside the realm of free support. See Consulting if you'd like our help moving forward.