Compat with native unserialize()?

Just wondering: what happens when doing `igbinary_unserialize(serialize('foo'))`?
Is `igbinary_unserialize()` able to autodetect the native serialization format and forward the call to the native `unserialize()` function?
If not, how about adding it to help moving forward, e.g. migrating sessions from `serialize` to `igbinary` without having to purge existing sessions in the process?
