problem in php array replace null value with in same group id

i try to replace value of arrays in same group with that one has the value but its not work correctly you can see in the code below why?

function trace($val)
{
    echo "pre";
    print_r($val);
    echo "pre";
}
$rows = array(
                  开发者_运维知识库      array('a'=>'33333','b'=>'#3333','group'=>1),
                        array('a'=>'','b'=>'','group'=>1),
                        array('a'=>'','b'=>'','group'=>2),
                        array('a'=>'5555','b'=>'#werwe','group'=>2)
                        );
trace($rows);

$oldGroupId = -1;
        foreach($rows as &$row)
            foreach($row as $column=>$fieldValue)
            {
                    if($row['group']!=$oldGroupId)
                        ${$row['group']}[$column]=0;
                    if( !is_null( $row[$column]  ) )
                        ${$row['group']}[$column]=$row[$column];
                    //@ in this place try to point to my dynamick variable pointer for change if change value frome previuse all value in array cahnge
                    $row[$column] = & ${$row['group']}[$column];
            }

trace($rows);
?>

the value in output:

Array
(
    [0] => Array
        (
            [a] => 33333
            [b] => #3333
            [group] => 1
        )

    [1] => Array
        (
            [a] => 
            [b] => 
            [group] => 1
        )

    [2] => Array
        (
            [a] => 
            [b] => 
            [group] => 2
        )

    [3] => Array
        (
            [a] => 5555
            [b] => #werwe
            [group] => 2
        )

)
Array
(
    [0] => Array
        (
            [a] => 
            [b] => 
            [group] => 1
        )

    [1] => Array
        (
            [a] => 
            [b] => 
            [group] => 1
        )

    [2] => Array
        (
            [a] => 5555
            [b] => #werwe
            [group] => 2
        )

    [3] => Array
        (
            [a] => 5555
            [b] => #werwe
            [group] => 2
        )

)

the value expected:

Array
(
    [0] => Array
        (
            [a] => 33333
            [b] => #3333
            [group] => 1
        )

    [1] => Array
        (
            [a] => 33333
            [b] => #3333
            [group] => 1
        )

    [2] => Array
        (
            [a] => 5555
            [b] => #werwe
            [group] => 2
        )

    [3] => Array
        (
            [a] => 5555
            [b] => #werwe
            [group] => 2
        )

)

update :

if this is not work please tell me another way for this reason ?

---

Start with

$rows = array(
    array('a'=>'33333','b'=>'#3333','group'=>1),
    array('a'=>'','b'=>'','group'=>1),
    array('a'=>'','b'=>'','group'=>2),
    array('a'=>'5555','b'=>'#werwe','group'=>2)
);

Create a temporary variable to hold the overall info of each group.

$groups = array();

Then add each non-empty value to the array.

foreach ($rows as &$row) {
    if (!isset($groups[$row['group']])) {
        $groups[$row['group']] = array();
    }
    $groups[$row['group']] += array_filter($row);
}

Finally, replace each row with the overall info of the group.

foreach ($rows as &$row) {
    $row = $groups[$row['group']];
}

Output: See at Codepad