Fix registration of internal readonly child classes

[kocsismate]

Currently, internal classes are registered with the following code:

INIT_CLASS_ENTRY(ce, "InternalClass", class_InternalClass_methods);
class_entry = zend_register_internal_class_ex(&ce, NULL);
class_entry->ce_flags |= ...;

This has worked well so far, except if InternalClass is a readonly class. It is because some inheritance checks are run by zend_register_internal_class_ex, before ZEND_ACC_READONLY_CLASS is added to ce_flags.

The issue is fixed by adding a zend_register_internal_class_with_flags() zend API function that stubs can use from now on. This function makes sure to add the flags before running any checks. Since the new API is not available in lower PHP versions, gen_stub.php has to keep support for the existing API for PHP 8.4-.

The fix is tested in #14461 where I originally found the issue.

[kocsismate]

@nielsdos @iluuu1994 May I get a review from you?

[nielsdos]

Changes seem fine, just 2 remarks/questions about the stub generator

[nielsdos]

Suggested change

	$code .= "\tclass_entry = zend_register_internal_class_with_flags(&ce, " . (isset($this->extends[0]) ? "class_entry_" . str_replace("\\", "_", $this->extends[0]->toString()) : "NULL") . ", " . (implode("", $flagCodes) ?: 0) . ");\n";
	$code .= "\tclass_entry = zend_register_internal_class_with_flags(&ce, " . (isset($this->extends[0]) ? "class_entry_" . str_replace("\\", "_", $this->extends[0]->toString()) : "NULL") . ", " . ($flags ?: 0) . ");\n";

[nielsdos]

Can use $flags too.
Also, don't you need to check if $flags !== "" here?

[kocsismate]

Yes, I definitely should have checked it.

[iluuu1994]

The changes look correct to me.