PHP 8.2 [AllowDynamicProperties] showcase

This utility is intended to showcase what's contained in the PHP 8.2 AllowDynamicProperties RFC.

This is to avoid Deprecation Warnings on PHP 8.2 when using Dynamic Properties: PHP Deprecated: Creation of dynamic property Class::$attribute is deprecated.

This repository is intended to show how to globally solve the PHP Deprecated: Creation of dynamic property is deprecated with minor code changes, thus allowing dynamic properties with no warnings.

TL;DR

To make a Class compatible with Dynamic Attributes, follow the below example, that is purposedly using a namespace.

Pay attention: in a project using namespaced classes, you will HAVE TO add the use \AllowDynamicProperties; to make this work. Otherwise, PHP won't know what "AllowDynamicProperties" is. Under the hoods, in fact, the attribute set above the Class definition is using The AllowDynamicProperties class, that really is a Final Class itself.

<?php
namespace App\Classes;

/**
 * Use the fully-qualified AllowDynamicProperties, otherwise the #[AllowDynamicProperties] attribute on "MyClass" WILL NOT WORK.
 */
use \AllowDynamicProperties;

#[AllowDynamicProperties]
class MyClass
{
    /**
     * Dynamic attributes will work with no deprecation warnings
     */
    public function __construct()
    {
        $this->first_name = 'George';
        $this->last_name = 'Orwell';
    }
}

class MyExtendedClass extends MyClass 
{
    /**
     * Even if "MyExtendedClass" is not using #[AllowDynamicProperties], it extends "MyClass", that is using it.
     * Dynamic attributes will work with no deprecation warnings
     */
    public function __construct()
    {
        parent::__construct();
    }
}

Why bother?

In PHP 8.2 and later, setting a value to an undeclared class property is deprecated, and emits a deprecation notice the first time the property is set during the lifetime of the application execution. There are legitimate use cases of dynamic properties, such as value objects derived from a dynamic JSON response, or configuration objects that allow arbitrary values. (reference: php.watch)

IMHO, Deprecating dynamic properties sucks. The votation of 2021-11-26 finished with a favor of 52 votes, with only 25 that were not convinced (as I am.)

Anyway, the #[AllowDynamicProperties] attribute is an effective workaround to let this feature work and not trigger any E_DEPRECATED warnings.

The tests are intended to let the reader know how to implement the #[AllowDynamicProperties] in various scenarios.

How to run the test

You'll have to use PHP 8.2 binary. Here is the list of steps to run all the tests.

1. composer install
2. /usr/bin/php8.2 test --verbose all to run all the tests in verbose mode (dumps objects)
3. /usr/bin/php8.2 test all to run all the tests
4. /usr/bin/php8.2 test [deprecated|allowDynamicPropertiesTest1|allowDynamicPropertiesTest1OnExtended|allowDynamicPropertiesTest2|allowDynamicPropertiesTest2OnExtended] to specifically run a single test

If you only want a readable, simple, single-file test that showcases everything, use showcase.php:

1. /usr/bin/php8.2 showcase.php

What to expect from the different tests

1. deprecated: you will get E_DEPRECATED warnings
2. allowDynamicPropertiesTest1: you shold not get E_DEPRECATED warnings. Dynamic Properties are set within the class constructor.
3. allowDynamicPropertiesTest1OnExtended: you shold not get E_DEPRECATED warnings. This test extends the AllowDynamicPropertiesTest1 class.
4. allowDynamicPropertiesTest2: you should not get E_DEPRECATED warnings. Dynamic Properties are set via calling a specific setProps() method.
5. allowDynamicPropertiesTest2OnExtended: you should not get E_DEPRECATED warnings. This test extends the AllowDynamicPropertiesTest2 class.
6. stackOverflowUser706420Test: you will get E_DEPRECATED warnings. This test is intended to demonstrate that StackOverflow's user706420 is not correct in his comment left here: in fact, his statement is true only on non-namespaced contexts. In a namespaced context, you'll always need the fully-qualified use \AllowDynamicProperties; statement.