Here some_arr[] has two values, but after POST-ing the resulting array seems like it is repeating itself.

Example:
<!-- input -->
<form method="post">
<input type="checkbox" name="some_arr[]" value="aa" CHECKED>
<input type="checkbox" name="some_arr[]" value="bb" CHECKED>
<input type="submit">
</form>

<!-- result after post -->
var_dump($some_arr):
array(3) {
  [0]=>
  string(2) "aa"
  [1]=>
  string(15) "bbsome_arr[]=aa"
  [2]=>
  string(2) "bb"
}

When I replace the POST wit GET it works fine.