Description:
------------
Perhaps there's a way to do this via other PHP trickery, but I'd like to be able to create a small ZIP file in-memory, without any filesystem requirement.

In potentially producing hundreds of these small zip files per second, I'd rather not thrash my drives.

Reproduce code:
---------------
## Contrived Example

$zip = new ZipArchive;
$res = $zip->open();
if ($res === true) {
        $zip->addFromString('data', '<datastream>');
        $zip->close();
        echo $zip;
}