I installed Drupal 8 on MAMP Pro with PHP 7. I am getting this warning in my Drupal reports page:
PHP OPcode caching Not enabled
PHP OPcode caching can improve your site's performance considerably. It is highly recommended to have OPcache installed on your server.
I looked in MAMP's PHP 7 ini file and I see this code which seems to be related to OPcode caching.
[OPcache] MAMP_OPcache_MAMP opcache.memory_consumption=128 opcache.interned_strings_buffer=8 opcache.max_accelerated_files=4000 opcache.revalidate_freq=60 opcache.fast_shutdown=1 opcache.enable_cli=1
So I am not sure if I need to do anything else to enable it, it seems to be enabled based on the code above. I googled around and could not find any specific documentation with regard to MAMP and PHP OPcode caching.