Edit: Skip this and scroll down for a proper fix!
Just tried installing MongoDB support for PHP on Kubuntu 15.10 via pecl and ran into the following error message which caused the installation to fail:
configure: error: Cannot find OpenSSL's libraries
While this can probably be fixed using some magickery, in my case, I did not want SSL support on a dev server. I just wanted to get the fucker up and running. To this end, I discovered that the issue was that I was using:
pecl install mongodb