I will post this to Tutorials when I get a working Author account here but in the mean time - here is valuable info for those who are thinking about going Debian 10 and PHP 7. https://sami.mattila.eu/tech/php Have fun.
There is fine tutorial about that: https://www.howtoforge.com/tutorial...fig-3-from-debian-packages-on-debian-8-and-9/ If you do not run ISPConfig, you can ignore the ISPConfig parts of the tutorial. An alternative is to compile PHP 5.6 yourself on that host, there is a tutorial for that also.
You should always keep the default PHP version of the system for ISPconfig. However, for Debian10 the default is php7.3 ;-)