Download and install MAMP: https://www.mamp.info/

Before starting MAMP, you'll want to make a couple of configurations in MAMP/bin/php/php7.4.33/conf/php.ini. Note that your version of PHP in the file path may be different.

First, turn on error reporting so that you see errors if you do something wrong. For me, this was on line 472.

; http://php.net/display-errors
display_errors = On

Next, disable OPcache to prevent a caching behavior that may get in the way of development by commenting out the opcache settings. A comment starts with a ;. For me, these settings were on lines 1892 - 1898.

[OPcache]
; zend_extension="/Applications/MAMP/bin/php/php7.4.33/lib/php/extensions/no-debug-non-zts-20190902/opcache.so"
;   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