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ActiveLibrary[Utility & Helpers](/categories/utility)
texthtml/vo-identity
====================
Make comparing Value Objects easier & safer
00PHPCI passing
Since Feb 6Pushed 3mo ago1 watchersCompare
[ Source](https://github.com/texthtml/vo-identity)[ Packagist](https://packagist.org/packages/texthtml/vo-identity)[ RSS](/packages/texthtml-vo-identity/feed)WikiDiscussions main Synced 1mo ago
READMEChangelogDependenciesVersions (2)Used By (0)
VO Identity
===========
[](#vo-identity)
Make comparing Value Objects for equality easier & safer.
Installation
============
[](#installation)
```
composer req texthtml/vo-identity
```
Usage
=====
[](#usage)
```
final readonly class UserID
{
use TH\VOIdentity\Identity;
private function __construct(private int $i) {}
}
$ua = UserID::of(42);
$ub = UserID::of(42);
$uc = UserID::of(24);
assert($ua === $ub); // $ua & $ub reference the same object so they can be compared with `===`
assert($ua !== $uc);
```
How does it work?
=================
[](#how-does-it-work)
The `Identity` trait implements a named constructor `::of()` that takes the same arguments as the Value Object constructor. And return the same instance of the Value Object when an identical Value Object than a previous one would have been created.
To identify identical Value Object, `$vo->identity()` is called and should return a valid array key. A weak reference to the object will be kept in a cache using that key. The next time an object would be created, if a reference with that ley exists it will be returned. The default implementation of `$vo->identity()` is using `serialize($vo)` to generate the the ID. This is valid but can generate large string and be time consuming for large objects. For better performance, it is recommended to override it with a specialized implementation. e.g.:
```
final readonly class UserID
{
use TH\VOIdentity\Identity;
private function __construct(private int $id) {}
protected function identity(): int
{
return $this->id;
}
}
```
You can also opt-in to implemented `inputIdentity()` to compute the key from the constructor arguments, and thus avoid having to construct the Value Object if not needed. e.g.:
```
final readonly class UserID
{
use TH\VOIdentity\Identity;
private function __construct(private int $id) {}
protected function inputIdentity(int $id): int
{
return $id;
}
}
```
Garbage collection
------------------
[](#garbage-collection)
By keeping only a weak reference to the first created instance, this let PHP able to garbage collect the Value Objects when they are not referenced anywhere else and avoid memory leaks.
Requirements
============
[](#requirements)
To work properly a few rules must be respected:
- The object must be immutable and final
- The constructor should be pure (calling it with the same argument should always produce the same result)
Notes
=====
[](#notes)
Cloning
-------
[](#cloning)
It's not allowed to clone a Value Object using `Identity`. Doing so would defeat the purpose by creating a new instance of a Value Object having the same inner value.
Unserializing
-------------
[](#unserializing)
PHP `__unserialize()` can't be implemented in a way that an already existing instance of an object is returned instead of a new instance. Because of that it's not allowed to `unserialize()` a previously `serialize()`'d Value Objects. Of course, serializing and unserializing them with other tools is possible (e.g. with the Symfony Serializer, or as a custom Doctrine type.
Exporting
---------
[](#exporting)
It is possible to serialize a Value Object with `var_export()` and `eval()` the corresponding export to get a PHP instance. If the object properties doesn't match the constructor `__set_state()` will need to be overriden.
### Health Score
19
—
LowBetter than 10% of packages
Maintenance54
Moderate activity, may be stable
Popularity0
Limited adoption so far
Community9
Small or concentrated contributor base
Maturity14
Early-stage or recently created project
Bus Factor1
Top contributor holds 68.2% of commits — single point of failure
How is this calculated?**Maintenance (25%)** — Last commit recency, latest release date, and issue-to-star ratio. Uses a 2-year decay window.
**Popularity (30%)** — Total and monthly downloads, GitHub stars, and forks. Logarithmic scaling prevents top-heavy scores.
**Community (15%)** — Contributors, dependents, forks, watchers, and maintainers. Measures real ecosystem engagement.
**Maturity (30%)** — Project age, version count, PHP version support, and release stability.
### Community
Maintainers
[mathroc](/maintainers/mathroc)
---
Top Contributors
[![text-html-renovate[bot]](https://avatars.githubusercontent.com/u/6465918?v=4)](https://github.com/text-html-renovate[bot] "text-html-renovate[bot] (15 commits)")[](https://github.com/mathroc "mathroc (7 commits)")
### Embed Badge
```
[](https://phpackages.com/packages/texthtml-vo-identity)
```
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