Array to string convertion error

Received the following error today:

What PHP version are you using?

PHP 7.0.33-1~dotdeb+8.1


Completely off-topic, but I feel the need to mention it:
PHP 7.0 isn’t maintained anymore since 3 Dec 2018 and doesn’t recieve security updates anymore.

So if you want to continue using inofficial backports of up-to-date PHP versions take a look at (which is maintained by the maintainer of the official debian PHP packages)
This is also recommended by dotdeb, as they stopped maintaining PHP packages.

Thanks for the heads up. Upgraded to 7.3, will see how it goes.

This is what I get now: