Use php.ini in a subdirectory?

Hello, I'm installing Magento 2 in a domain managed by cPanel, I changed the memory_limit requirements in the domain's php.ini but I can't figure out how to apply it in the subdirectories (the theme I installed have a builtin importer that uses composer to install some dependancies but it stops and throws an out of memory error and the max memory is the one set in the global php.ini). I read something about suPHP_ConfigPath but I can't make it work properly (error 500). Thanks in advance for your help, have a great day :)