PHP SplObjectStorage::key() Method: Usage and Examples

Reports the numeric index of the current storage iterator entry.

The examples focus on the operation itself, including the important distinction: current reads the object at the cursor.

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

SplObjectStorage::key()

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.

Example 1: Basic Use

SplObjectStorage retains object identity and can associate independent information with each object; it is not keyed by the label property.

<?php
$one = (object) ["label" => 'alpha'];
$two = (object) ["label" => 'beta'];
$three = (object) ["label" => 'gamma'];
$store = new SplObjectStorage();
$store[$one] = "pending";
$store[$two] = "approved";
$store->rewind();
$store->next();
echo $store->key();

Output from a successful local PHP 8.4 run:

1

Example 2: Checking Behavior

SplObjectStorage retains object identity and can associate independent information with each object; it is not keyed by the label property.

<?php
$one = (object) ["label" => 'red'];
$two = (object) ["label" => 'green'];
$three = (object) ["label" => 'blue'];
$store = new SplObjectStorage();
$store[$one] = "pending";
$store[$two] = "approved";
$store->rewind();
$store->next();
echo $store->key();

Output from a successful local PHP 8.4 run:

1

Example 3: Practical Example

SplObjectStorage retains object identity and can associate independent information with each object; it is not keyed by the label property.

<?php
$one = (object) ["label" => 'first'];
$two = (object) ["label" => 'second'];
$three = (object) ["label" => 'third'];
$store = new SplObjectStorage();
$store[$one] = "pending";
$store[$two] = "approved";
$store->rewind();
$store->next();
echo $store->key();

Output from a successful local PHP 8.4 run:

1

Important Behavior and Edge Cases

It is not the object ID; use spl_object_id for a numeric object identity token.

Comparison with Related Approaches

Common Beginner Mistakes

Key Takeaways

• Reports the numeric index of the current storage iterator entry.
• It is not the object ID; use spl_object_id for a numeric object identity token.
• current reads the object at the cursor.

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