mac上的nginx + php7.4环境突然报502错误，所有项目工程都无法访问，猜测是php-fpm未能成功启动，尝试启动php-fpm，显示如下错误：
zhb@192 ~ % php-fpm
dyld[3193]: Library not loaded: /opt/homebrew/opt/icu4c/lib/libicuio.71.dylib
Referenced from: <8D2684CB-6F2B-3C4E-9A5F-E22409A68226> /opt/homebrew/Cellar/php@7.4/7.4.33/sbin/php-fpm
Reason: tried: '/opt/homebrew/opt/icu4c/lib/libicuio.71.dylib' (no such file), '/System/Volumes/Preboot/Cryptexes/OS/opt/homebrew/opt/icu4c/lib/libicuio.71.dylib' (no such file), '/opt/homebrew/opt/icu4c/lib/libicuio.71.dylib' (no such file), '/usr/local/lib/libicuio.71.dylib' (no such file), '/usr/lib/libicuio.71.dylib' (no such file, not in dyld cache), '/opt/homebrew/Cellar/icu4c/73.2/lib/libicuio.71.dylib' (no such file), '/System/Volumes/Preboot/Cryptexes/OS/opt/homebrew/Cellar/icu4c/73.2/lib/libicuio.71.dylib' (no such file), '/opt/homebrew/Cellar/icu4c/73.2/lib/libicuio.71.dylib' (no such file), '/usr/local/lib/libicuio.71.dylib' (no such file), '/usr/lib/libicuio.71.dylib' (no such file, not in dyld cache)
zsh: abort sudo php-fpm
卸载重装php7.4
#卸载
brew uninstall php@7.4
#安装
brew install php@7.4
卸载没问题，安装出错
Error: php@7.4 has been disabled because it is a versioned formula!
这是因为php7.4版本官方已经不再维护，所以Hombrew将该PHP版本移出了repository，因此安装失败。
尝试从第三方仓库中安装：
# 将第三方仓库加入brew
brew tap shivammathur/php
# 安装PHP
brew install shivammathur/php/php@7.4
重启php-frm
brew services restart shivammathur/php/php@7.4
问题解决
