最近寫SDK的時候需要用到object型別提示符，PHPStorm智慧提示說需要PHP7.2以上才能支援這種型別提示。
我一查我本機的PHP是7.1.30版本，於是考慮升級一下PHP版本。
首先要嘗試使用如下命令進行升級：
brew update
brew upgrade php@7.4
第一個遇到的報錯如下所示：
git -C /usr/local/Homebrew/Library/Taps/homebrew/homebrew-core fetch --unshallow
This restriction has been made on GitHub's request because updating shallow
clones is an extremely expensive operation due to the tree layout and traffic of
Homebrew/homebrew-core and Homebrew/homebrew-cask. We don't do this for you
automatically to avoid repeatedly performing an expensive unshallow operation in
CI systems (which should instead be fixed to not use shallow clones). Sorry for
the inconvenience!
然後按照提醒執行"git -C /usr/local/Homebrew/Library/Taps/homebrew/homebrew-core fetch --unshallow"命令還會報錯：
fatal: dumb http transport does not support shallow capabilities
由此懷疑homebrew-core的源可能因為一些不可抗力的原因無法正常使用，從而導致fetch操作失敗。可以考慮換成國內的源，編寫shell如下所示：
# 切換到homebrew-core目錄下
cd "$(brew --repo)/Library/Taps/homebrew/homebrew-core"
# 設定homebrew源為國內的中科大映象
git remote set-url origin https://mirrors.ustc.edu.cn/homebrew-core.git
# 更新homebrew-core
git -C /usr/local/Homebrew/Library/Taps/homebrew/homebrew-core fetch --unshallow
執行之後可以看到如下輸出，然後就可以順利執行brew update了。
remote: Enumerating objects: 539863, done.
remote: Counting objects: 100% (539826/539826), done.
remote: Compressing objects: 100% (194417/194417), done.
remote: Total 530481 (delta 341532), reused 521981 (delta 333211)
Receiving objects: 100% (530481/530481), 191.29 MiB | 9.18 MiB/s, done.
Resolving deltas: 100% (341532/341532), completed with 8120 local objects.
安裝php7.4的方法很簡單，可以使用原始碼下載編譯的方法：
brew install --build-from-source php@7.4
可以看到大量輸出，最後沒有報錯就可以完成php7.4的安裝啦。
要讓終端裡面之前的PHP版本切換成功還需要在.bash_profile中設定環境變數，新增如下語句：
export PATH="/usr/local/opt/php@7.4/bin:$PATH"
export PATH="/usr/local/opt/php@7.4/sbin:$PATH"
最後執行source ~/.bash_profile命令完成生效操作。
為了確認是否真的生效，可以執行如下命令php -v
得到輸出如下即為正確:
PHP 7.4.15 (cli) (built: Feb 21 2021 20:08:10) ( NTS )
Copyright (c) The PHP Group
Zend Engine v3.4.0, Copyright (c) Zend Technologies
with Zend OPcache v7.4.15, Copyright (c), by Zend Technologies
參考的資料如下：