Description:
------------
It seems that PDO->sqliteCreateAggregate() (or at least Example #1) isn't working as documented .
Documentation and Example #1 talks against using a copy of $context, but this function from the example doesn't work, unless you return $context:
function max_len_step(&$context, $rownumber, $string) 
{
    if (strlen($string) > $context) {
        $context = strlen($string);
    }
}


Reproduce code:
---------------
The code block from Example #1


Expected result:
----------------
array(1) {
  [0]=>
  array(2) {
    ["max_len(a)"]=>
    string(1) "5"
    [0]=>
    string(1) "5"
  }
}


Actual result:
--------------
array(1) {
  [0]=>
  array(2) {
    ["max_len(a)"]=>
    NULL
    [0]=>
    NULL
  }
}