What is the matter with what you already have http://www.sitepoint.com/community/t/passing-an-id-to-query-where-in-a-table/105606/11.
As far as I can tell output would be something like this.
Array
(
[0] => Array
(
[userid] => 1
[effort] => 3
)
[1] => Array
(
[userid] => 1
[effort] => 4
)
)