brew install php@7.4
brew link --force --overwrite php@7.4
brew services start php@7.4
export PATH="/usr/local/opt/php@7.4/bin:$PATH"
export PATH="/usr/local/opt/php@7.4/sbin:$PATH"

To enable PHP in Apache add the following to httpd.conf and restart Apache:
    LoadModule php7_module /usr/local/opt/php@7.4/lib/httpd/modules/libphp7.so

    <FilesMatch \.php$>
        SetHandler application/x-httpd-php
    </FilesMatch>

Finally, check DirectoryIndex includes index.php
    DirectoryIndex index.php index.html

The php.ini and php-fpm.ini file can be found in:
    /usr/local/etc/php/7.4/

php@7.4 is keg-only, which means it was not symlinked into /usr/local,
because this is an alternate version of another formula.

If you need to have php@7.4 first in your PATH, run:
  echo 'export PATH="/usr/local/opt/php@7.4/bin:$PATH"' >> ~/.profile
  echo 'export PATH="/usr/local/opt/php@7.4/sbin:$PATH"' >> ~/.profile

For compilers to find php@7.4 you may need to set:
  export LDFLAGS="-L/usr/local/opt/php@7.4/lib"
  export CPPFLAGS="-I/usr/local/opt/php@7.4/include"


To have launchd start php@7.4 now and restart at login:
  brew services start php@7.4
Or, if you don't want/need a background service you can just run:
  php-fpm