Dynamic (non-explicitly declared) properties are deprecated as of PHP 8.2 and are expected to become a fatal error in PHP 9.0.
There are a number of ways to mitigate this:
* If it is an accidental typo for a declared property: fix the typo.
* For known properties: declare them on the class.
* For unknown properties: add the magic `__get()`, `__set()`, et al. methods to the class or let the class extend `stdClass` which has highly optimized versions of these magic methods built in.
* For unknown ''use'' of dynamic properties, the `#[AllowDynamicProperties]` attribute can be added to the class. The attribute will automatically be inherited by child classes.
In this case, the `$is_overloaded` property and the `$_f` property fall in the “known property” category. In both cases, these are being set in the `__construct()` method of the class they apply to.
The `$_post` property appears to be a typo however. The `$_post` property looks to be unused, while there is an undeclared integer `$_pos` (“position”) property, which is used throughout the class and used by the child classes.
Reference: [https://wiki.php.net/rfc/deprecate_dynamic_properties PHP RFC: Deprecate dynamic properties].
Follow-up to [11626], [12174], [53557], [53558], [53850], [53851], [53852], [53853], [53854], [53856], [53916], [53935], [53936], [53937], [53938], [53942], [53945], [53948], [53949], [53952], [53953].
Props jrf, antonvlasenko, costdev.
See #56033.
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