PHPCompatibility should check for PHP 8.3 and 8.4 compatibility

[hostep]

Description

We currently only check for PHP 8.1 and 8.2 compatibility, which is pretty outdated. Especially now that Magento 2.4.8 will be released soon and will only support PHP 8.3 and 8.4

Expected behavior

Detect potential problems with PHP 8.3 and 8.4 in code scanned with this tool

Benefits

Finding problems in Magento core codebase and pull requests before they are released, using static analysis.

Additional information

I see 2 problems:

• The Magento fork https://github.com/magento/PHPCompatibilityFork is very outdated, I really don't know why we can't use the original tool: https://github.com/PHPCompatibility/PHPCompatibility (yes, it hasn't had a stable version for many years, but using dev-develop as composer requirement works very good in my experience)
• We currently have the PHPCompatibility testVersion setup to only scan for PHP 8.1 and 8.2 versions, see:

  magento-coding-standard/Magento2/ruleset.xml

  Line 775 in d7ece6d

  <config name="testVersion" value="8.1-8.2"/>

  
  Changing this line probably won't help as the first bullet point points out that the Magento fork of this ruleset is very outdated and probably doesn't contain many checks against PHP 8.3/8.4 in contrast to the upstream version

[m2-assistant]

Hi @hostep. Thank you for your report.
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Add a comment to assign the issue: @magento I am working on this

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[fredden]

Related: #487