public static function post($url, $payload, $contentType = 'Content-Type: application/json') {
		// TODO move constants to global configuration file
		$ch = curl_init ( $url );
		curl_setopt ( $ch, CURLOPT_CUSTOMREQUEST, "POST" );
		curl_setopt ( $ch, CURLOPT_POSTFIELDS, $payload );
		curl_setopt ( $ch, CURLOPT_RETURNTRANSFER, true );
		curl_setopt ( $ch, CURLOPT_HTTPHEADER, array (
				$contentType,
				'Content-Length: ' . strlen ( $payload ) 
		) );
		$result = curl_exec ( $ch );
		return $result;
	}