NOTE: This is a major release of PHP. With PHP 7, many things change.
Check if your software is compatible with PHP 7.2 and update, if not. 
Information on the migration from PHP 5.6 to 7.2 can be found here:
https://secure.php.net/manual/en/migration70.php
https://secure.php.net/manual/en/migration71.php
https://secure.php.net/manual/en/migration72.php