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

Question

I have a table with the following structure. There are currently 9 students enrolled in 3 classes (classes 01, 16 and 52), with 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 is the array with all current classes:
$classes_array = array ( [0] => 01 [1] => 52 [2] => 16 )
Using this array I would like to go through the mysql table and create a multidimensional array with the classcodes used as first level keys:
Array
(
[01] => Array
(
[0] => D3kcIvyp
[1] => DdIhBc
[2] => 2vx0KV
)
[52] => Array
(
[0] => 9p1PxWCV
[1] => RnmfH1WE
[2] => MSTBEv
)
[16] => Array
(
[0] => Yp4J3o
[1] => fWQ5Oo
[2] => 6sxw3u
)
)
foreach ($classes_array as $key => $value)
{
$sql = "SELECT studentcode FROM table WHERE classcode = '$classes_array[$key]'";
$result = mysql_query($sql) or die();
while($data = mysql_fetch_array($result))
{
$studentcodes_array[] = $data['studentcode'];
}
foreach ($studentcodes_array as $studentcodeskey => $studentcodesvalue)
{
$multid_array[$value][] = $studentcodesvalue;
}
}
Using the code above, unfortunately I don't get the array I would like to get. I get this 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 is wrong with my code? Can anybody help me with this?

Answer 1

You never initialise $studentcodes_array so it is remembering all the values from your previous loops.
Try adding $studentcodes_array = array(); before your while.