Add #[NoSerialize] attribute support to prevent property serialization.

[dkulyk]

RFC: https://wiki.php.net/rfc/no_serialize_attribute

This PR introduces a new attribute, #[NoSerialize], that can be
applied to class properties to explicitly exclude them from
serialization when using PHP’s built-in serialization mechanisms.

Motivation

When developing complex objects, it’s often necessary to exclude
specific properties from serialization — for example, resources,
closures, database connections, or transient caches.
Currently, developers must manually implement __serialize() /
__sleep() to filter these properties, which can lead to boilerplate
code and potential maintenance errors.

Adding a native attribute would provide a simple and declarative way
to express this intention directly in code.

class Example
{
    public string $name;

    #[NoSerialize]
    public $connection; // e.g., PDO, socket, or any transient resource
}

When serialize($example) is called, $connection would be excluded automatically.

Benefits

• Reduces boilerplate for common use cases.
• Makes serialization intent explicit and self-documenting.
• Simplifies framework and library code that relies on serialization

[dkulyk]

RFC: https://wiki.php.net/rfc/no_serialize_attribute

[TimWolla]

Should this be closed in favor of #20163?

[dkulyk]

Should this be closed in favor of #20163?

Those are different RFCs.

#20163 forbids class to serialization.
This PR/RFC allows ignore properties or objects on serialization.

I'm working on the 3rd RFC, which should logically gather all these things.

[calebdw]

@dkulyk, any update on this? I was looking for such an attribute so I didn't have to overload __sleep and I came across this---would be very useful!