1. Download Composer

Head over to the Composer website and copy the install code. It should be 4 lines of code, copy them all. Paste all 4 lines into your terminal.

After running that command, there will be a file composer.phar in the current directory. You could use that command like this:

php composer.phar install

2. Installing Globally

To make composer available globally, allowing you to type composer install anywhere, you have to move the recently downloaded composer.phar to local user’s bin folder:

mv composer.phar /usr/local/bin/composer

3. Open your shell profile

What shell are you using?

Using bash? (Default shell on Mac OS <10.14, 2002-2019)

Open your ~/.bash_profile

open -e  ~/.bash_profile

Using zsh? (Default shell on Mac OS 10.15+, 2019-Present)

Open your ~/.zshrc

open -e  ~/.zshrc

4. Add alias to composer

Add an alias to point at the composer.phar you moved into /usr/local/bin/*.

In your .zshrc or .bash_profile add the following line. It will create an alias of composer that can be used globally.

alias composer="php /usr/local/bin/composer"

5. Use composer globally

After restarting your terminal you will be able to access composer like below:

composer install

There are a few ways to accomplish this and an alias method is a simplistic approach. For a more consistent global usage (with other global installs) you should look into adding /usr/local/bin to your PATH, see here.