Mac の PHP 7.1 を PHP 7.3 にする

$ brew search php@7
==> Formulae
php@7.1                                 php@7.2                                 php@7.3

==> php
To enable PHP in Apache add the following to httpd.conf and restart Apache:
    LoadModule php7_module /usr/local/opt/php/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/7.3/

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


$ php -v
PHP 7.1.23 (cli) (built: Feb 22 2019 22:08:13) ( NTS )
Copyright (c) 1997-2018 The PHP Group
Zend Engine v3.1.0, Copyright (c) 1998-2018 Zend Technologies

$ cd /usr/local/opt

$ ls php*
php@ php@7.3@


$ cd php@7.3/bin

$ which php
/usr/bin/php

$ sudo mv /usr/bin/php /usr/bin/php7.1

$ sudo cp php /usr/bin/php

$ php -v
PHP 7.3.8 (cli) (built: Aug  6 2019 23:15:07) ( NTS )
Copyright (c) 1997-2018 The PHP Group
Zend Engine v3.3.8, Copyright (c) 1998-2018 Zend Technologies
    with Zend OPcache v7.3.8, Copyright (c) 1999-2018, by Zend Technologie