Re: [RFC] Deprecate dynamic properties

Hi Nikita Popov, > I'd like to propose the deprecation of "dynamic properties", that is > properties that have not been declared in the class (stdClass and > __get/__set excluded, of course): > > https://wiki.php.net/rfc/deprecate_dynamic_properties > > This has been discussed in various forms in the past, e.g. in > https://wiki.php.net/rfc/locked-classes as a class modifier and > https://wiki.php.net/rfc/namespace_scoped_declares / > > https://github.com/nikic/php-rfcs/blob/language-evolution/rfcs/0000-language-evolution.md > as a declare directive. > > This RFC takes the more direct route of deprecating this functionality > entirely. I expect that this will have relatively little impact on modern > code (e.g. in Symfony I could fix the vast majority of deprecation warnings > with a three-line diff), but may have a big impact on legacy code that > doesn't declare properties at all. I'd had some concerns. It might be too soon after your addition of WeakMap. https://www.php.net/weakmap was introduced in PHP 8.0 (and WeakReference in 7.4), so applications/libraries fixing the deprecation may need to drop support for php 7.x early. Applications attempting to polyfill a WeakMap in earlier PHP versions would potentially leak a lot of memory in php 7.x. - I don't know how many minor versions to expect before 9.0 is out - Is it feasible for a developer to create a native PECL polyfill for WeakMap for earlier PHP versions that has a subset of the functionality the native weak reference counting does? (e.g. to only free polyfilled weak references when cyclic garbage collection is triggered and the reference count is 1). Additionally, it makes it less efficient (but still feasible) to associate additional fields with libraries or native classes/PECLs you don't own (especially for circular data structures), especially if they need to be serialized later. (it isn't possible to serialize WeakMap, and the WeakMap would have fields unrelated to the data being serialized) I guess you can have a wrapper class that iterates over a WeakMap to capture and serialize the values that still exist in SplObjectStorage, though. (Though other languages do just fine without this functionality) I'm not sure if a library owner would want to change their class hierarchy to extend stdClass (to avoid changing the behavior of anything using $x instanceof stdClass) and the attribute/trait approach might be more acceptable to library owners. E.g. https://github.com/vimeo/psalm/blob/master/src/Psalm/Internal/Analyzer/Statements/Expression/Call/FunctionCallAnalyzer.php would set a dynamic property $stmt->pure in PhpParser\Node\Expr\FuncCall $stmt in a vendor dependency on php-parser. Regards, Tyson