NGINX 1.11.5 (Mainline) breaks purge

Chris, thanks for your post. fastcgi_cache_purge is not part of the official NGINX open source project, and never has been. This directive is available as an unsupported third party module (1), or as part of NGINX Plus (2).

root@xx:~# nginx -v
nginx version: nginx/1.11.4
root@xx:~# nginx -t -c ~/nginx-purge.conf 
nginx: [emerg] unknown directive "fastcgi_cache_purge" in /home/xx/nginx-purge.conf:47
nginx: configuration file /home/xx/nginx-purge.conf test failed

I know the rtCamp team well (the authors of this plugin) and they compile their own NGINX build (3).

(1) https://github.com/FRiCKLE/ngx_cache_purge/
(2) https://www.nginx.com/products/content-caching-nginx-plus/
(3) https://easyengine.io/wordpress-nginx/tutorials/single-site/fastcgi-cache-with-purging/

Disclaimer: I work for NGINX, Inc.