Failing builds and PHP 8 support

[hibariya]

Bug report

Describe the bug

It looks like some PHP samples don't support PHP 8. Since the latest composer Docker image bundles PHP 8.0.2, composer failed to satisfy the dependencies in this build in accept-a-card-payment. Considering the cause, I think the other repositories may also have the same issue.

This is the detailed error messages:

Loading composer repositories with package information
Installing dependencies (including require-dev) from lock file
Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - Installation request for vlucas/phpdotenv v3.4.0 -> satisfiable by vlucas/phpdotenv[v3.4.0].
    - vlucas/phpdotenv v3.4.0 requires php ^5.4 || ^7.0 -> your PHP version (8.0.2) does not satisfy that requirement.

To Reproduce

https://github.com/stripe-samples/accept-a-card-payment/runs/1972142343

Expected behavior

The build passes.

Additional context

As for accept-a-card-payment, this PR (stripe-archive/accept-a-card-payment#58) will fix the issue for without-webhooks. However, we will need similar changes on using-webhooks, too.

Also, we could make CI use PHP 7 for now.

[hibariya]

I noticed that after removing the composer.lock, composer install completes without errors. Also, I couldn't see this error when running tests on checkout-one-time-payments which does not have composer.lock in the repository. Maybe we could just remove or update the lock files in accept-a-card-payment?

Here's the steps I did to reproduce the error on my local machine:

(in stripe-samples/accept-a-card-payment)
$ cd decline-on-card-authentication/server/php-slim/
$ md5sum composer.lock 
f86a60eade59b11c36205b830e7fb151  composer.lock
$ docker run --rm -it --workdir=/work -v $PWD:/work composer:1.10 /bin/bash
bash-5.1# composer install
Loading composer repositories with package information
Installing dependencies (including require-dev) from lock file
Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - Installation request for vlucas/phpdotenv v3.4.0 -> satisfiable by vlucas/phpdotenv[v3.4.0].
    - vlucas/phpdotenv v3.4.0 requires php ^5.4 || ^7.0 -> your PHP version (8.0.2) does not satisfy that requirement.

After removing composer.lock, the installation completed successfully:

bash-5.1# rm composer.lock 
bash-5.1# composer install
Loading composer repositories with package information
Updating dependencies (including require-dev)
Nothing to install or update
Writing lock file
Generating autoload files
4 packages you are using are looking for funding.
Use the `composer fund` command to find out more!
bash-5.1# 
exit
$ md5sum composer.lock
e8e154af97d620a731d6aad724bc9029  composer.lock

[cjavilla-stripe]

yeah feel free to remove composer.lock. That seems peaceful

[hibariya]

Thanks. I created a PR that removes the lock files: stripe-archive/accept-a-card-payment#69