Can't delete media that is in use via api, even with forceDelete = 1

You will want to use form_params with calls that use application/x-www-form-urlencoded instead of the multipart.

so something like:

    $response = $guzzle->request('DELETE', 'http://192.168.0.26/api/library/1223', [
        'headers' => [
            'Authorization' => 'Bearer ' . $token,
            'Content-type' => 'application/x-www-form-urlencoded'
        ],
        'form_params' => [
            'forceDelete' => 1
        ]
    ]);