Whenever an eZ Publish solution is upgraded, all caches must be cleared in a proper way. This should be done from within a system shell:
Navigate into the new eZ Publish directory.Run the script using the following shell command:
cd /<ezp5-root>/ezpublish_legacy/; php bin/php/ezcache.php --clear-all --purge. Purging ensures that the caches are physically removed. When the "--purge" parameter is not specified, the caches will be expired but not removed.
Note: Sometimes the script is unable to clear all cache files because of restrictive file/directory permission settings. Make sure that all cache files have been cleared by inspecting the contents of the various cache sub-directories within the "var" directory (typically the "var/cache/" and "var/<name_of_siteaccess>/cache/" directories). If there are any cache files left, you need to remove them manually.
Please have in mind that, after the upgrade to a major version of eZ Publish, you will need to perform regular updates with composer.