I have recently got a mac an am not used to developing on a mac at all.
I have MAMP Pro 1.9.6.1. I did a locate on php.ini
and got this:
On my mac, running MAMP I have a few locations that would be the likely php.ini, so I edited the memory_limit to different values in the 2 suspected files, to test which one effected the actual MAMP PHP INFO page details. By doing that I was able to determine that this was the correct php.ini: /Applications/MAMP/bin/php/php7.2.10/conf/php.ini