switching PHP and Drush versions for Drupal 7 and Drupal 9

#!/bin/bash
#Switch between PHP 7.4 and 8.0 and Drush Version 8 and 11

# To use this script download this file and name it switch-php.sh
# and give it the correct permissions
# You can then run ./switch-php  
# with the argument 7.4 or just ./switch-php
# For example ./switch-php 7.4

## First need to download PHP Versions 
## brew tap shivammathur/php
## brew install shivammathur/php/php@8.1
## brew install shivammathur/php/php@7.4
## confirm PHP 7.4 is not in the bash_profile path

#Switch to PHP 7.4 and Drush 8.x
if [[ $1 == "7.4" ]];
  then
 echo "------------------ PHP 7.4 ------------------------"
   brew unlink PHP
   brew link --force --overwrite php@7.4

  # Remove the current version of drush.
    composer global remove drush/drush
  # Install drush version 8
    composer global require drush/drush:8.x

else
  # Switch to PHP 8.1 and Drush 11.
   echo "------------------ PHP 8.1 ------------------------"
   brew unlink PHP
   brew link --force --overwrite php@8.1

  # Remove the current version of drush.
  composer global remove drush/drush
  # Install drush version 11
  composer global require drush/drush


fi

  # Show Me
  echo "------------------------------------"
  drush status
  php --version