Swapping elements in an array according to some criteria - php

Question

I am trying to swap elements in my array according to some criteria.
For example, my array has "blocks" which have to move together, for example move +1 spot in the array.
// bubble sort
foreach ($cleanCard as $key=>$value) {
$cleanCard = handleGroupDirection('down', $value['groupID'], $cleanCard);
}
The $cleanCard array passed as parameter above looks like:
$cleanCard = array(
'0' => array(
'groupID' => 1,
'value' => 'T PHONE'
),
'1' => array
(
'groupID' => 1,
'value' => ''
),
'2' => array
(
'groupID' => 1,
'value' => 'C CELL'
),
'3' => null,
'4' => array
(
'groupID' => 0,
'value' => 'EMAIL'
)
);
As you can see in this array, the element at key #3 is empty, which means that the group should move down 1 spot (even a grouped item that has no value...). The empty key stays in the array.
The resulting array should look like:
Array
(
[0] =>
[1] => Array
(
[groupID] => 1
[value] => T PHONE
)
[2] => Array
(
[groupID] => 1
[value] =>
)
[3] => Array
(
[groupID] => 1
[value] => C CELL
)
[4] => Array
(
[groupID] => 0
[value] => EMAIL
)
)
My code looks like:
function handleGroupDirection($direction, $groupID, $card) {
$groupArr = array_map(function($field) { return $field['groupID']; }, $card);
$groupKeys = array_keys($groupArr, $groupID);
$firstFieldOfGroupIndex = $groupKeys[0];
$lastFieldOfGroupIndex = end($groupKeys);
switch ($direction) {
case 'down':
if ($lastFieldOfGroupIndex+1 >= count($card)) break;
if ($card[$lastFieldOfGroupIndex+1] == null) {
// move each field of the group down, starting
// from the last field in the group
for ($i = count($groupKeys); $i >= 0; $i--) {
$currentCardIndex = $groupKeys[$i];
$card[$currentCardIndex+1] = $card[$currentCardIndex];
}
// make the first field of the group null, the null spot we took is now basically going in front of the group
$card[$firstFieldOfGroupIndex] = null;
}
break;
}
return $card;
}
Haven't had success with this code yet.
Edit:
I get the notices:
NOTICE Undefined offset: 3 on line number 20
$currentCardIndex = $groupKeys[$i];
NOTICE Undefined index: on line number 21
$card[$currentCardIndex+1] = $card[$currentCardIndex];
And the current array I get is:
Array
(
[0] =>
[1] => Array
(
[groupID] => 1
[value] => T PHONE
)
[2] =>
[3] => Array
(
[groupID] => 1
[value] => C CELL
)
[4] => Array
(
[groupID] => 0
[value] => EMAIL
)
)
[2] Shouldn't be empty !