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

Returns an iterator over live object keys and their metadata values.

The examples focus on the operation itself, including the important distinction: offsetGet retrieves one object's metadata without traversing the map.

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::getIterator(): Iterator

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.

Declared return type: Iterator. 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];
foreach ($metadata->getIterator() as $object => $info) { echo $object->name . ":" . $info["score"]; }

Output from a successful local PHP 8.4 run:

Ari:2

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];
foreach ($metadata->getIterator() as $object => $info) { echo $object->name . ":" . $info["score"]; }

Output from a successful local PHP 8.4 run:

Bo:3

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];
foreach ($metadata->getIterator() as $object => $info) { echo $object->name . ":" . $info["score"]; }

Output from a successful local PHP 8.4 run:

Cam:4

Important Behavior and Edge Cases

The map never keeps an object alive solely because it is a key.

Comparison with Related Approaches

Common Beginner Mistakes

Key Takeaways

• Returns an iterator over live object keys and their metadata values.
• The map never keeps an object alive solely because it is a key.
• offsetGet retrieves one object's metadata without traversing the map.

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