---
date: 2020-11-10
id: 7cdfd822-29cd-4b53-996f-7e7f618f754a
title: PHP Weak Maps
---

# Description

Weak maps[^1] allow creating a map from objects to arbitrary values
(similar to SplObjectStorage) without preventing the objects that are
used as keys from being garbage collected. If an object key is garbage
collected, it will simply be removed from the map. This will save a lot
of headaches for people writing things like ORMs.

# Syntax

``` php
class Foo
{
    private WeakMap $cache;

    public function getSomethingWithCaching(object $obj): object
    {
        return $this->cache[$obj]
           ??= $this->computeSomethingExpensive($obj);
    }
}
```

# Footnotes

[^1]: <https://wiki.php.net/rfc/weak_maps>