error occurred in getting checkbox value

First, when you use input name="array[]", you can't really trust indexes, if you select first and third item from one array, and second and fourth item from second array, you get:

PHP Code:

$array1[
    0 => 'value for item 1',
    1 => 'value for item 3'
];

$array2[
    0 => 'value for item 2',
    1 => 'value for item 4'
]; 


So as fist thing, you ought to find a way to include related metadata (in your case, matching certid) somehow in the name/array that comes back.