storing multiselect value.htm

<input name="sample[]" type="checkbox" value="1"> Test 1
<input name="sample[]" type="checkbox" value="2"> Test 2
<input name="sample[]" type="checkbox" value="4"> Test 3
<input name="sample[]" type="checkbox" value="8"> Test 4
<input name="sample[]" type="checkbox" value="16"> Test 5

===========

1. DB relationship


tblsample   
---------------
id    |   name
1     |   Test 1
2     |   Test 2
4     |   Test 3
8     |   Test 4
16    |   Test 5


tblanswer
---------------
id    |   desc
1     |   lorem ipsum
2     |   dolor sit amet

tblselectionmatch
---------------
id    | sample_id   | answer_id
1     |     2       |     2
2     |     8       |     2
3     |     16      |     2
4     |     8       |     1


2. store as string (Comma deliminated / json / serialize etc )
Get array value and convert it to string

tblanswer
---------------
id    |   desc            |   selection
1     |   lorem ipsum     |    8
2     |   dolor sit amet  |    2, 8, 16


3. bitmask
Get array value and sum it

tblanswer
---------------
id    |   desc            |   selection
1     |   lorem ipsum     |    8
2     |   dolor sit amet  |    26

4. Any other options?..

Don't see the need for tblselectionmatch. Can simply add tblsample.id in tblanswer, unless of course there's another layer of data granularity that you need to store but not shown here.