Centos 6 sys with php5.3.3, php5.6 and php7.0.
Virtual Host set with php5.3.3 Just installed WP.
Adding a plugin I get:
Adaptive Images Error — PHP GD image library missing
The PHP GD image library is not detected in your server. ...
php -m | grep -i gd
rpm -qa | grep php
I could successfully installed the same plugin in another WP installation (different virtual host, same server and php version) I have long time ago.
I don't realize what's going on. I created the virtual host using Virtualmin.
Also switched from 5.3.3 to 7.0 php version but GD wasn't found too