PHP spl_object_id() Function: Usage and Examples

Returns a numeric identity token for a live object.

The examples focus on the operation itself, including the important distinction: spl_object_hash returns a string identity token instead of an integer.

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

spl_object_id(object $object): int

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: int. Read the behavior notes for important cases such as empty collections and destructive iteration.

Example 1: Basic Use

An object ID is unique among simultaneously live objects. Do not persist it as a stable database identifier.

<?php
$one = new stdClass();
$two = new stdClass();
echo spl_object_id($one) === spl_object_id($two) ? "same" : "different";

Output from a successful local PHP 8.4 run:

different

Example 2: Checking Behavior

An object ID is unique among simultaneously live objects. Do not persist it as a stable database identifier. The additional check illustrates stable live-object identity or identity after cloning.

<?php
$one = new stdClass();
$two = new stdClass();
echo spl_object_id($one) === spl_object_id($two) ? "same" : "different";
echo " same token=" . (spl_object_id($one) === spl_object_id($one) ? "yes" : "no");

Output from a successful local PHP 8.4 run:

different same token=yes

Example 3: Practical Example

An object ID is unique among simultaneously live objects. Do not persist it as a stable database identifier. The additional check illustrates stable live-object identity or identity after cloning.

<?php
$one = new stdClass();
$two = new stdClass();
echo spl_object_id($one) === spl_object_id($two) ? "same" : "different";
$clone = clone $one;
echo " clone different=" . (spl_object_id($clone) !== spl_object_id($one) ? "yes" : "no");

Output from a successful local PHP 8.4 run:

different clone different=yes

Important Behavior and Edge Cases

IDs can be reused after object destruction and are not persistent identifiers.

Comparison with Related Approaches

Common Beginner Mistakes

Key Takeaways

• Returns a numeric identity token for a live object.
• IDs can be reused after object destruction and are not persistent identifiers.
• spl_object_hash returns a string identity token instead of an integer.

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