"error: #error "OpenCV 4.x+ requires enabled C++11 support"

Question

How can I fix this?

I installed OpenCV 4.1.0 without a problem on Centos 7.6 following this guide:

https://linuxize.com/post/how-to-install-opencv-on-centos-7/

Now I'm trying to install php-opencv

https://github.com/hihozhou/php-opencv

And it's failing when I make. (Under the Compile and install php-opencv extension header on that link).

Many thanks, COMPLETELY out of my depth here.