Composer reports incorrect PHP version in php:7.4.*-fpm-alpine3.15

[josefsabl]

Now this is very strange. Although php -v reports correct php version (7.4.28) when trying to use composer to install dependencies it tells me I have PHP 8.0.16.

Steps to reproduce:

1. Run the container

docker run -it php:7.4.28-fpm-alpine3.15 /bin/sh

2. Run this script

apk add composer
echo '{
  "name": "test/test",
  "version": "0.0",
  "authors": [],
  "require": {
    "php": "^7.4.0"
  }
}' > composer.json
composer install

3. Result:

Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - Root composer.json requires php ^7.4.0 but your php version (8.0.16) does not satisfy that requirement.

The problem seems to be with the latest version of alpine and not the php version. I tried for two last versions of both:

php:7.4.28-fpm-alpine3.15 bug
php:7.4.27-fpm-alpine3.15 bug
php:7.4.28-fpm-alpine3.14 ok
php:7.4.27-fpm-alpine3.14 ok

[GreyXor]

Hello,
when you apk add composer, apk also add php8 dependency as you can see here.
Then when you run composer it uses in fact the php8 dependency from composer and not the one that is installed in the image.

If you want to use the PHP of the docker image. then you can simply add the path to the binary before calling composer
/usr/local/bin/php /usr/bin/composer.phar

Depending on the context, it may be appropriate to use composer via a multi-stage Dockerfile. Moreover the composer image is perfect for that.

[josefsabl]

Well, I am speechless. This makes the composer package in the alpine completely useless as it breaks its usage. They better remove it completely to at least prevent confusion of users. We are thinking about walking away from alpine. This lunacy is one more reason to speed up the decision.

I am installing the composer like this now (in case somebody stumbles upon this):

COPY --from=composer:2.2.7 /usr/bin/composer /usr/bin/composer

Thank you for your explanation.

[tianon]

Indeed -- see #542; when you apk add composer (or any other PHP package) in the php base image, you're installing a second version of PHP (as explained).

I'm not sure whether Alpine has similar pinning behavior such that we could block installation of Alpine's PHP packages in the image as we did for Debian in #542, but I'd be +1 on doing so if such a feature exists.

[GreyXor]

You can also install composer in this way
RUN sh -c "$(curl -sSL https://github.com/mlocati/docker-php-extension-installer/releases/latest/download/install-php-extensions)" -c @composer