After doing the following steps the PHP settings were set to 5.6 instead of default.
yum install http://mirror.de-labrusse.fr/nethserver/nethserver-php-scl/nethserver-remi-phpscl-1.0.0-1.ns6.sdl.noarch.rpm
then
yum install http://mirror.de-labrusse.fr/nethserver/nethserver-php-scl/nethserver-php-scl-1.0.3-1.ns6.sdl.x86_64.rpm --enablerepo=remi-phpscl
Hopefully you didn’t meant that I had expected that. 
I know that software developing is not as easy as many people think.
I want only help with testing because my joomla install needed a higher php version.
Cool, that you could sort it out!
Many thanks for help.
It worked now with 5.3 till 5.6. PHP 7.0 has still the error.
If I could do some further tests to help you, please let me know. 