'fb' => 726310296 ), 'lists' => array( 'list-1' => 1, 'list-2' => 1, 'list-3' => 0 ) )); //update existing user by email or create new user using email address $response = $client->saveUser('*****@*****.**', array( 'key' => 'email', 'lists' => array( 'list-1' => 0 // optout from list-1 ) )); // get user by Sailthru ID $fields = array( 'keys' => 1, 'vars' => 1, 'activity' => 1 ); $response = $client->getUseBySid("4e2879472d7acd6d97144f9e", $fields); // get user by Custom key $response = $client->getUserByKey("*****@*****.**", 'email', $fields); } catch (Sail_Client_Exception $e) { // deal with exception }