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
]
]);