I recently put together a wordpress site on some web space I have. There is a copy of C panel on it which has a thing called PHP Selector which allows you to choose the version of PHP and what settings within that work. I am currently running Wordpress 5.0.3 with PHP 7.2 (with the default settings selected) and it seems to be working fine.

If I change PHP to version 7.3 it completely breaks things! Either giving an error 500 or error 503 depending on which options within PHP 7.3 are ticked. Wordpress aim to be functional with v7.3 after next release - Wordpress announcement

As soon as the version of PHP is changed back to v7.2 it works immediately.

The options that I have ticked in v7.2 that work with 5.0.3 are the following - PHP 7.2 settings