PHP WeakMap::offsetUnset() Method: Usage and Examples

Removes the mapping for a specific object instance.

The examples focus on the operation itself, including the important distinction: offsetSet attaches metadata; offsetUnset detaches it.

What It Does

Use the examples below to observe the behavior on a small dataset before extending it to application code.

Syntax and Return Value

WeakMap::offsetUnset($object): void

The displayed signature describes the API or identifies any correction or optional dependency. When a parameter is optional, supply it only when the task requires it.

Parameters

• object: required.

Declared return type: void. Read the behavior notes for important cases such as empty collections and destructive iteration.

Example 1: Basic Use

The map tracks an object only while another strong reference keeps it alive; keys use identity rather than a name string.

<?php
$user = (object) ["name" => 'Ari'];
$other = (object) ["name" => "guest"];
$metadata = new WeakMap();
$metadata[$user] = ["score" => 2];
$metadata->offsetUnset($user);
echo count($metadata);

Output from a successful local PHP 8.4 run:

0

Example 2: Checking Behavior

The map tracks an object only while another strong reference keeps it alive; keys use identity rather than a name string.

<?php
$user = (object) ["name" => 'Bo'];
$other = (object) ["name" => "guest"];
$metadata = new WeakMap();
$metadata[$user] = ["score" => 3];
$metadata->offsetUnset($user);
echo count($metadata);

Output from a successful local PHP 8.4 run:

0

Example 3: Practical Example

The map tracks an object only while another strong reference keeps it alive; keys use identity rather than a name string.

<?php
$user = (object) ["name" => 'Cam'];
$other = (object) ["name" => "guest"];
$metadata = new WeakMap();
$metadata[$user] = ["score" => 4];
$metadata->offsetUnset($user);
echo count($metadata);

Output from a successful local PHP 8.4 run:

0

Important Behavior and Edge Cases

This does not destroy the object if references exist elsewhere.

Comparison with Related Approaches

Common Beginner Mistakes

Key Takeaways

• Removes the mapping for a specific object instance.
• This does not destroy the object if references exist elsewhere.
• offsetSet attaches metadata; offsetUnset detaches it.

Use WeakMap::offsetUnset when its documented behavior matches the problem. Test the relevant edge cases in your own runtime before deploying it.