Check PHP8 compatibility

[pfefferle]

https://wordpress.slack.com/archives/C3D6T7F8Q/p1593596189094100

[getsource]

Doing this step by step.

Step one:

• I tested the plugin in PHP8 and it seems to work as expected so far.

Next:

• Get reporter's automated tests running with PHP8
• Check to see that test runner works as expected with PHP8: Update for PHP 8 Compatibility phpunit-test-runner#121

[desrosj]

Potentially related: https://twitter.com/ottokekalainen/status/1322275628662595585?s=21

First 👏 and thanks to Seravo for adding PHP8 testing. ❤️

I'm am trying to figure out why the tests fail for them but not Core on Travis, and wondering if something in here is causing the failure.

[ottok]

If it helps debugging, here is the same commit tested with both PHP 7.4 (pass) and PHP 8.0 (failure):

https://make.wordpress.org/hosting/test-results/r49470/seravobot-r49470/

The PHP 8.0 was the latter run, so it's results remain on the result page.

Since the result page does not show any detailed log, I have attached them manually.
php80.txt
php74.txt

[getsource]

There might be more problems, but I think the main issue is that the test runner is using PHPUnit 5.6.x:
WordPress/phpunit-test-runner#121 (comment)

[ottok]

If somebody makes a PR or test branch on this topic, I am happy to run the test runner based on code from an alternative branch to verify if the proposed changes fix the issue.

[kittenkamala]

Old ticket, needs a refresh

Most recent php is v 8.4 https://php.watch/versions/8.4

Current WP supports up to 8.2 w beta for 8.3 and 8.4 https://make.wordpress.org/core/handbook/references/php-compatibility-and-wordpress-versions/

Issue may no longer be relevant as composer was configured to pull in the latest version based on server environment here WordPress/phpunit-test-runner#132

I think we can close this out.