I was finally able to resolve this. The Auth library with the old api is messed up. It doesn't sign the params, headers and more importatnly the post_data correctly in case of a POST. The MyspaceID sdk has the correct Auth library, atleast so far it has worked with POST. If you're still working with the old library, get rid of the OAuth.php and copy the latest from MyspaceID sdk. Get the CryptUtil.php as well becuase OAuth is dependent on it.
Then change the do_post in myspaceapi of your old library-
from-
$req = OAuthRequest::from_consumer_and_token($this->oauth_consumer, $this->oauth_token, HttpMethodType::$GET,$this->resource_base . $this->resource_uri, $headers);
to
$req = OAuthRequest::from_consumer_and_token($this->oauth_consumer, $this->oauth_token, HttpMethodType::$POST, $this->resource_base.$this->resource_uri, null, $headers, $post_data);
you'll have to make changes in the _do_post function of BaseAPI as well but that should be self explanatory. let me know if someone needs help.