PHP RFC: Change Directory class to behave like an opaque object

• Version: 0.1
• Date: 2024-09-14
• Author: Gina Peter Banyard girgias@php.net
• Status: Under Discussion
• Target Version: PHP 8.5
• Implementation: https://github.com/php/php-src/pull/15886
• First Published at: https://wiki.php.net/rfc/directory-opaque-object

The Directory class is probably the first instance of what we now call an “opaque object”. Opaque objects are normally the result of converting resources to objects, which in general implies, being final, being not serializable, not constructible via new, cannot be cast, and to not implement any methods. However, as this class has existed since PHP 4 none of these things are formally implemented.

Valid instances of this class are created by calling the dir() function. But one can create a broken instance by just using new Directory(), which is visible if one tries to call one of its methods.

As it seems likely that we will repurpose this class when converting directory resources to objects; we think it makes sense to already convert this class to behave like an opaque object.

We propose to make the following changes to the Directory class:

• Make it final
• Throw an Error when doing new Directory()
• Prevent cloning instances of Directory
• Ban serialization of it via the @not-serializable doc comment on the class stub
• Ban creating dynamic properties on an instance of Directory via the @strict-properties doc comment on the class stub

It will no longer be possible:

• to extend the Directory class
• clone, serialize, or create dynamic properties on an instance of Directory
• instantiate Directory directly via the new keyword

Next minor version, i.e. PHP 8.5.

As per the voting RFC a yes/no vote with a 2/3 majority is needed for this proposal to be accepted.

Voting started on 2024-XX-XX and will end on 2024-XX-XX.