How to fix "dyld: Library not loaded"?

I ran the following command php -v, and instead of getting the version, I got the following error:

dyld: Library not loaded: /usr/local/opt/libffi/lib/libffi.6.dylib
  Referenced from: /usr/local/bin/php
  Reason: image not found

I tried many things I found online, but the following is what did the trick for me.

How to fix the error

1. I ran brew update. For me, everything was up to date.

2. I ran brew upgrade.

   I got the following error:

    Removing: /usr/local/Cellar/php/7.4.4... (517 files, 76MB)
    Error: Directory not empty @ dir_s_rmdir - /usr/local/Cellar/php/7.4.4
   

3. I ran brew cleanup, and I got a similar error:

   Error: Directory not empty @ dir_s_rmdir - /usr/local/Cellar/nginx/1.17.9
   

4. I ran sudo rm -R /usr/local/Cellar/nginx/1.17.9.

5. I ran brew cleanup again, and once again, I got a similar error.

    Error: Directory not empty @ dir_s_rmdir - /usr/local/Cellar/php/7.4.4
   

   This is the same error as my step 2.

6. I ran sudo rm -R /usr/local/Cellar/php/7.4.4.

7. I then ran brew cleanup again. It seemed like everything worked.

    Pruned 0 symbolic links and 15 directories from /usr/local
   

8. Finally, I tried php -v again, and this time it worked!

Summary

If you are getting a "dyld: Library not loaded > Reason: image not found" error, try running brew update and brew upgrade. If you get a Error: Directory not empty, try removing that directory using sudo rm -R.