php --version Alias设置在Mac上出错了

I am developing a PHP project. I am using Mac OS X now. To be honest, this is the first time developing a PHP project using Mac. I am a Windows. I installed PHP using brew by running the following command.

brew install php

It gave me the php latest version, 7+. For my project, I need to use php version 5.6. So, I installed another PHP by running this command.

brew install php56

Up until this point when I enter "php --version" in the terminal, it is showing that I am using php version 7+. I found some solution to change php version and so I used one of them and run this command.

 alias php='/usr/local/etc/php/5.6/php'

After running that command, when I type in "php --version" in the terminal, it is showing this error.

-bash: /usr/local/etc/php/5.6/php: No such file or directory

Now, I cannot use any PHP on my mac right now. How can I fix the error, please?