Symfony 4.4 can generate a preloading file for your application in the cache directory. The generated file name includes both the environment and kernel names
During container compilation (e.g. when running the cache:clear command), Symfony generates a file with the list of classes to preload in the var/cache/ directory. Rather than use this file directly, use the config/preload.php file that is created when using Symfony Flex in your project:
; php.ini
opcache.enable=1
opcache.preload=/path/to/project/config/preload.php