I put composer, but it doesn't respond.

I put composer by referring to the following. https://usado.jp/spdsk/2018/08/20/post-4221/ But no matter what

bash: composer: command not found```

 It became.
 The cause was that I was doing it as the root user.
 When I exited with exit and hit composer, it reacted.

 I just didn't read the explanation well, but I learned that this is the case.