How to install GMP extension for PHP 7.4.2 using MAMP

mamp-php-gmp.md

Installing GMP extension for PHP 7.4 using MAMP

You have to build the GMP extension from the PHP source code. First install Autoconf and GMP using Homebrew.

brew install autoconf gmp

Download and unpack PHP.

http://php.net/get/php-7.4.2.tar.bz2/from/a/mirror

$ cd php-7.4.2/ext/gmp
$ /Applications/MAMP/bin/php/php7.4.2/bin/phpize
$ ./configure --with-php-config=/Applications/MAMP/bin/php/php7.4.2/bin/php-config
$ make
$ make install

Add the extension loading config to php.ini in /Applications/MAMP/bin/php/php7.4.2/conf.

extension=gmp.so

Restart MAMP servers and verify extension is loaded in the phpinfo() report.

This worked @tomhapbia, thanks!