class.implementsInternalClass

Code example

<?php declare(strict_types = 1);

namespace Vendor {
	/** @internal */
	class InternalClass {}
}

namespace App {
	class MyClass implements \Vendor\InternalClass {}
}

Why is it reported?

The class uses a class in its implements clause that is marked as @internal. Internal types are not part of the package's public API and may change or be removed without notice in future versions.

A class cannot implement another class in PHP -- only interfaces can be implemented. This code is invalid regardless of the @internal annotation.

How to fix it

Use a public (non-internal) interface instead:

-class MyClass implements \Vendor\InternalClass {}
+class MyClass implements \Vendor\PublicInterface {}

If no public alternative exists, consider reaching out to the package maintainers to request a public API for your use case.