Might this just be an issue with some of our older PHP images? I ran some builds using the image tags currently listed in Docker Hub and Composer seems to be available in those. Just not in circleci/php:7.1.5-browsers as noted above.
- exampel 1: circleci/php:latest
- example 2: circleci/php:7.1-browsers
- example 3: circleci/php:7.0-browsers