brew link の php バージョン変更の失敗について話しましょう

php 5.6
php 7.4
php 8.0

$ brew unlink php@8.0 && brew link php@7.4
Unlinking /usr/local/Cellar/php/8.0.3... 0 symlinks removed.
Linking /usr/local/Cellar/php@7.4/7.4.16... 264 symlinks created.
$ php -v

brew update
brew upgrade

https://github.com/shivammathur/homebrew-php

Warning: Already linked: <Cellar Path>
To relink:
  brew unlink <formula> && brew link <formula>

brew unlink php@7.3
brew link --overwrite --force php@7.3

apache brew services restart httpd
nginx brew services restart nginx

To enable PHP in Apache add the following to httpd.conf and restart Apache:
    LoadModule php7_module /usr/local/opt/php@7.0/lib/httpd/modules/libphp7.so
    <FilesMatch \.php$>
        SetHandler application/x-httpd-php
    </FilesMatch>
Finally, check DirectoryIndex includes index.php
    DirectoryIndex index.php index.html
The php.ini and php-fpm.ini file can be found in:
    /usr/local/etc/php/7.0/
php@7.0 is keg-only, which means it was not symlinked into /usr/local,
because this is an alternate version of another formula.
If you need to have php@7.0 first in your PATH run:
  echo &#39;export PATH="/usr/local/opt/php@7.0/bin:$PATH"&#39; >> ~/.zshrc
  echo &#39;export PATH="/usr/local/opt/php@7.0/sbin:$PATH"&#39; >> ~/.zshrc
For compilers to find php@7.0 you may need to set:
  export LDFLAGS="-L/usr/local/opt/php@7.0/lib"
  export CPPFLAGS="-I/usr/local/opt/php@7.0/include"
To have launchd start shivammathur/php/php@7.0 now and restart at login:
  brew services start shivammathur/php/php@7.0
Or, if you don&#39;t want/need a background service you can just run:
  php-fpm