php - Creating a multidimensional array using an array and loop through mysql table -

i have table following structure. there 9 students enrolled in 3 classes (classes 01, 16 , 52), 3 enrollments in each class.

studentcode | classcode   ------------------------- d3kcivyp    | 01   ddihbc      | 01   2vx0kv      | 01   9p1pxwcv    | 52   rnmfh1we    | 52   mstbev      | 52   yp4j3o      | 16   fwq5oo      | 16   6sxw3u      | 16   

this array current classes:

$classes_array = array ( [0] => 01 [1] => 52 [2] => 16 ) 

using array go through mysql table , create multidimensional array classcodes used first level keys:

array (     [01] => array         (             [0] => d3kcivyp             [1] => ddihbc             [2] => 2vx0kv         )      [52] => array         (             [0] => 9p1pxwcv             [1] => rnmfh1we             [2] => mstbev         )      [16] => array         (             [0] => yp4j3o             [1] => fwq5oo             [2] => 6sxw3u         ) )   foreach ($classes_array $key => $value) {      $sql = "select studentcode table classcode = '$classes_array[$key]'";     $result = mysql_query($sql) or die();     while($data = mysql_fetch_array($result))     {         $studentcodes_array[] = $data['studentcode'];     }      foreach ($studentcodes_array $studentcodeskey => $studentcodesvalue)     {         $multid_array[$value][] = $studentcodesvalue;     } } 

using code above, unfortunately don't array get. instead:

array (     [01] => array         (             [0] => d3kcivyp             [1] => ddihbc             [2] => 2vx0kv         )      [52] => array         (             [0] => d3kcivyp             [1] => ddihbc             [2] => 2vx0kv             [3] => 9p1pxwcv             [4] => rnmfh1we             [5] => mstbev         )      [16] => array         (             [0] => d3kcivyp             [1] => ddihbc             [2] => 2vx0kv             [3] => 9p1pxwcv             [4] => rnmfh1we             [5] => mstbev             [6] => yp4j3o             [7] => fwq5oo             [8] => 6sxw3u         )  ) 

what wrong code? can me this?

you never initialise $studentcodes_array remembering values previous loops.

try adding $studentcodes_array = array(); before while.