Unable to resize SplfixedArray after being unserialized in PHP 8.2.15

[codex-m]

Description

The following code:

<?php
ini_set('display_errors', 1);
ini_set('display_startup_errors', 1);
ini_set('error_reporting', E_ALL);

echo "============" . "<br />";
echo "Testing in " . phpversion() . "<br />";
echo "============";
echo "<br /><br />";

/**
 * Create 5 items
 */
$array = new SplFixedArray(5);

/**
 * Get size
 * EXPECTED: 5
 */
$size = $array->getSize();
echo "Original size before serializing. Expected result is 5." . "<br />";
echo "Actual result: $size";
echo "<br /><br />";

/**
 * Serialize SPLFixedArray object
 */
$serialized = serialize($array);

/**
 * Unserialize SPLFixedArray object
 */
$array = unserialize($serialized);

/**
 * Get size
 * EXPECTED: 5
 */
$size = $array->getSize();
echo "Original size after serializing. Expected is still 5." . "<br />";
echo "Actual result is $size";
echo "<br /><br />";
   
/**
 * Resize SPLFixedArray to 6 items
 */
echo "Resizing array to 6 items" . "<br />";
$array->setSize(6);
/**
 * Get size after resize
 * EXPECTED: 6
 */
$size = $array->getSize();
echo "Updated size after resize. " . "<em>" . "Expected is 6." . "</em>" . "<br />";
echo "<strong>" . "Actual result is $size" . "</strong>";
echo "<br />";

Resulted in this output:

============
Testing in 8.2.15
============

Original size before serializing. Expected result is 5.
Actual result: 5

Original size after serializing. Expected is still 5.
Actual result is 5

Resizing array to 6 items
Updated size after resize. Expected is 6.
Actual result is 5

But I expected this output instead:

============
Testing in 8.2.15
============

Original size before serializing. Expected result is 5.
Actual result: 5

Original size after serializing. Expected is still 5.
Actual result is 5

Resizing array to 6 items
Updated size after resize. Expected is 6.
Actual result is 6

Additional notes:

• This is only reproducible with PHP 8.2.15.
• It works well with PHP 8.1/8.0/7.4.

I've checked the docs on changes with setSize() method with PHP 8.2. It does not mention that it cannot be used after unserializing. So I open this ticket as it could be a bug. Thank you!

PHP Version

PHP 8.2.15

Operating System

Ubuntu 22.04 LTS