Why is there an error in Joomla's registry.php file?

Question

PHP

Hello! For some reason, after migrating the Joomla site to VDS with PHP 7, many errors of this type appeared:
Notice: Array to string conversion in /var/www/test1/libraries/framework/Joomla/Registry/Registry.php on line 419
Almost in all errors there is a file /var/www/test1/libraries/framework/Joomla/Registry/Registry.php
How to fix this error?

Answer 1

Due to different syntax interpretation between php versions.
Update Joomla (maybe fixed) or rollback php.
And this is not a mistake, but a remark.