Fix build

[andrewmy]

• Fix a deprecation which made all the builds red;
• Add the PHP requirement to composer.json to prevent misunderstandings about the new syntax;
• Fix using a prophecy in a particular test;
• Update PHPUnit to v10 to avoid deprecations on PHP 8.2+

[Nyholm]

Do you know why the CI is red?

[andrewmy]

@Nyholm there were multiple reasons, check the updated description. And it's green now.

[Nyholm]

Great!

[andrewmy]

Thank you for the release! 🎉