Installing the now deprecated Homebrew php@7.1 on macOS

brew install php@7.1

To install the deprecated php@7.1 on macOS using Homebrew, run the following commands:
```bash  
git -C "$(brew — repo homebrew/core)" checkout d541efc^ — Formula/php@7.1.rb
brew install php@7.1
pecl install xdebug
pecl install igbinary
pecl install redis
```
If you are using PHPStorm as your IDE, you can configure xdebug by removing the extension lines added to your php.ini file by default and adding the following files to the `/usr/local/homebrew/etc/php/7.1/conf.d` folder. 
```ini
; ext-xdebug.ini
[xdebug]
zend_extension="/usr/local/homebrew/lib/php/pecl/20160303/xdebug.so"
xdebug.remote_enable=1
xdebug.remote_port="9000"
```
```ini
; ext-igbinary.ini
[xdebug]
extension="/usr/local/homebrew/lib/php/pecl/20160303/igbinary.so"
```
```ini
; ext-redis.ini
[xdebug]
extension="/usr/local/homebrew/lib/php/pecl/20160303/redis.so"
```
Make sure and update your PHP interpreter in PHPStorm to point at your homebrew PHP@7.1 install binary `/usr/local/homebrew/Cellar/php@7.1/7.1.33/bin/php`. Once seet, the above settings should allow you to use the PHP debugger in PHPStorm with the default settings.