Comment 2 for bug 1250159

In 13.10, "saucy", at least, it looks like php5-json is suggested by php5-common (http://packages.ubuntu.com/saucy/php5-common), but it is not a dependency. I suppose that this relationship wasn't strong enough for it to be pulled in when I ran "sudo tasksel install lamp-server".

So it looks like php5-common can run without it, but drush can't. :)