问题描述：

我透過 brew 安裝三種php版本

php 5.6
php 7.4
php 8.0

$ php -v

PHP 8.0.3 (cli) (built: Mar  4 2021 20:45:17) ( NTS )
Copyright (c) The PHP Group
Zend Engine v4.0.3, Copyright (c) Zend Technologies
    with Zend OPcache v8.0.3, Copyright (c), by Zend Technologies

停用8.0使用7.4

$ brew unlink [email protected] && brew link [email protected]
Unlinking /usr/local/Cellar/php/8.0.3... 0 symlinks removed.
Linking /usr/local/Cellar/[email protected]/7.4.16... 264 symlinks created.
$ php -v

還是一樣版本

我開新的終端機也是一樣8.0.3

PHP 8.0.3 (cli) (built: Mar  4 2021 20:45:17) ( NTS )
Copyright (c) The PHP Group
Zend Engine v4.0.3, Copyright (c) Zend Technologies
    with Zend OPcache v8.0.3, Copyright (c), by Zend Technologies

中規中矩操作了

這是哪裏有少設置了？

分析解决：

你可以尝试安装一个PHP选择器

brew update
brew upgrade

参考文档

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

安装指定php brew install shivammathur/php/[email protected]

链接php版本 brew link --overwrite --force [email protected]

如果出现报错

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

执行

brew unlink [email protected]
brew link --overwrite --force [email protected]

重启服务

apache brew services restart httpd
nginx brew services restart nginx

安装结果

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

欢迎讨论！

学习：《PHP教程》

以上就是聊聊brew link更换php版本失败问题的详细内容