lib/AmazonSNS.php
public function listSubscriptions($nextToken = null) {
		$params = array();

		if(!is_null($nextToken)) {
			$params['NextToken'] = $nextToken;
		}

		$resultXml = $this->_request('ListSubscriptions', $params);

		// Get subscriptions
		$subs = $resultXml->ListSubscriptionsResult->Subscriptions->member;

		$return = ['members' => $this->_processXmlToArray($subs)];

		if(isset($resultXml->ListSubscriptionsResult->NextToken)) {
			$return['nextToken'] = strval($resultXml->ListSubscriptionsResult->NextToken);
		}

		return $return;
	}
public function listSubscriptions($nextToken = null) {
		$params = array();

		if(!is_null($nextToken)) {
			$params['NextToken'] = $nextToken;
		}

		$resultXml = $this->_request('ListSubscriptions', $params);

		// Get subscriptions
		$subs = $resultXml->ListSubscriptionsResult->Subscriptions->member;

		$return = ['members' => $this->_processXmlToArray($subs)];

		if(isset($resultXml->ListSubscriptionsResult->NextToken)) {
			$return['nextToken'] = strval($resultXml->ListSubscriptionsResult->NextToken);
		}

		return $return;
	}
List subscriptions that user is subscribed to

@link http://docs.amazonwebservices.com/sns/latest/api/API_ListSubscriptions.html
@param string|null $nextToken [optional] Token to retrieve next page of results
@return array