Array index automatically starts at 1

I have 2 input types. I have 4 select boxes and 4 checkboxes with hidden fields. The checkboxes have the same name and the select boxes. After submitting, I do this:

var_dump(Input::get(checkboxname));
var_dump(Input::get(selectboxname));

Which outputs:

array(4) { 
  [1]=>   string(5) "value"   
  [2]=>   string(5) "value"  
  [3]=>   string(5) "value" 
  [4]=>   string(5) "value" 
} 
array(4) {  
  [0]=>   string(5) "value"  
  [1]=>   string(5) "value"   
  [2]=>   string(5) "value"
  [3]=>   string(5) "value" 
}

This is my select box:

<select name="selectboxname[]" >
//values in a complicated for loop that's not important but it works
</select>

This is my checkbox:

<input  type='hidden' value='othervalue' name='checkboxname[]'>
<input  type="checkbox" name="checkboxname[]" value="value">

In the arrays, the checkboxes have the index like: 1,2,3,4 and the selectboxes have 0,1,2,3. I have to get the indexes to match with eachother. I know normally the index starts at 0 so the selectboxes are doing it right. What is going wrong here?