Check boxes don't use arrays.
radio boxes are arrays...
for a check box you have a series of boxes, and each can be checked
eg,
<input type=checkbox name=colour1 value=red />red
<input type=checkbox name=colour2 value=green />green
<input type=checkbox name=colour3 value=blue />blue
whilst radio boxes work in arrays where there is an array of elements, but only one value is passed through to the results page.
<input type=radio name=colour value=red />red
<input type=radio name=colour value=green />green
<input type=radio name=colour value=blue />blue