Unset an multidimensional array by key

Question

$series = array();  

while($row = mysql_fetch_assoc($result)) { 
            $series[$row["data_id"]][] = $row; 
        } 

The output from a print_r on $series yields for two example series:

Array (

[1] => Array ( [0] => Array ( [id] => 1 [data_id] => 1 [time_id] => 1 [data] => 1 ) [1] => Array ( [id] => 2 [data_id] => 1 [time_id] => 2 [data] => 3 ) )

[2] => Array ( [0] => Array ( [id] => 6 [data_id] => 2 [time_id] => 1 [data] => 7 ) [1] => Array ( [id] => 7 [data_id] => 2 [time_id] => 2 [data] => 4 ) )

My question: how do I unset the multidimensional array so it contains only [data] and none of the other keys? I still want $series to contain [1] and [2] but I do not want the respective sub-arrays to contain any other keys other than [data] .

In fact, since I am reducing the subarrays to contain a single key, I would really like to get rid of the subarrays altogether so that I have two arrays:

$series[1] = array(1,3) and $series[2] = array(7,4)

Answer 1

Try this :

$series = array();  

while($row = mysql_fetch_assoc($result)) { 
            $series[$row["data_id"]][] = $row['data']; 
        } 

Answer 2

I think you can loop in your array and build a new one keeping only data details

$array = array ('1' => array ( '0' => array ( 'id' => 1, 'data_id' => 1, 'time_id' => 1, 'data' => 1 ), '1' => array ( 'id' => 2, 'data_id' => 1, 'time_id' => 2, 'data' => 3 ), ),
'2' => array ( '0' => array ( 'id' => 6, 'data_id' => 2, 'time_id' => 1, 'data' => 7 ), '1' => array ( 'id' => 7, 'data_id' => 2, 'time_id' => 2, 'data' => 4 ) ));

$i= 0;
$n= 0;
$series = array();
foreach($array as $dato)
{
    $series[$i] = array();
    foreach($dato as $data)
    {
        foreach($data as $key => $value)
        {
            if($key == 'data')
            {
                $series[$i][$n] = $value;
                $n++;
            }
        }
    }
    $n = 0;
    $i++;
}
var_dump($series);

This will output

array (size=2)
  0 => 
    array (size=2)
      0 => int 1
      1 => int 3
  1 => 
    array (size=2)
      0 => int 7
      1 => int 4    

Live demo