Upgrading from php5.6 to php7

[Jos Chrispijn]

I need to upgrade from php 5.6 to php 7.0.
Can someone tell me how I can do that best? Read a lot of solutionson 
the web, but all tell different from each other.

Would it be better to first deinstall php 5.6 and then start all over 
with php7?

Thanks, Jos