rearrange php multidimensional array according to id - arrays

Question

-I cannot figure out how to regroup this array accourding to ids.
This array comes from a mysql table. the number 17 and 20 are foreign keys in the table.
$orginal_arr =
Array
(
[0] => Array
(
[id] => 17
[content] => string...?
)
[1] => Array
(
[id] => 20
[content] => hello
)
[2] => Array
(
[id] => 20
[content] => string...?
)
[3] => Array
(
[id] => 20
[content] => string...string...??
)
[4] => Array
(
[id] => 17
[content] => string...
)
[5] => Array
(
[id] => 17
[content] => string...
)
);
I want to convert the above $orginal_arr array to the following $desired_arr array.
$desired_arr = Array (
[0] => Array
(
[17] => Array
(
[0] => string...?
)
)
[1] => Array
(
[20] => Array
(
[0] => hello
[1] => string...?
[2] => string... string...??
)
)
[2] => Array
(
[17] => Array
(
[0] => string...
[1] => string...
)
)
);
so far I am trying the following approach:
function group_by_key($key, $data)
{
$result = array();
$j = 0;
foreach ($data as $val) {
if (array_key_exists($key, $val)) {
$result[$val[$key]][$j] = $val;
} else {
$result[""][] = $val;
}
$j++;
}
return $result;
}
$desired_arr = group_by_key("id", $orginal_arr);
$desired_arr2 = array();
foreach ($desired_arr as $index => $item) {
$desired_arr2 += $item;
}
echo "<pre>";
print_r($desired_arr2);
echo "</pre>";
the output:
Array
(
[0] => Array
(
[id] => 17
[content] => string...?
)
[4] => Array
(
[id] => 17
[content] => string...
)
[5] => Array
(
[id] => 17
[content] => string...
)
[1] => Array
(
[id] => 20
[content] => hello
)
[2] => Array
(
[id] => 20
[content] => string...?
)
[3] => Array
(
[id] => 20
[content] => string...string...??
)
)
- Thank you very much.

Answer 1

As I said in my comment, I'm not familiar to PHP syntax anymore so this will be pseudo code.
I would do it in 2 steps,
first I want this result
$temp_arr =
Array
(
[0] => Array
(
[id] => 17
[contents] => Array(
[0] => string...?
)
)
[1] => Array
(
[id] => 20
[contents] => Array(
[0] => hello
[1] => string...?
[2] => string...string...??
)
)
...
...
);
See, I kept the Object structure with id and contents (with a final S).
then it will be easier to check the id as it is directly accessible
$temp_array = Array();
foreach ($original_array as $element) {
$last = end($temp_array);
if ($last && $element->id == $last->id) {
// add to the last $temp_array element
$temp_array[count($temp_array)-1]->contents[] = $element->content;
}
else {
// create a new $temp_array element
$temp_array[] = Array(
"id" => $element->id,
"contents => Array(
$element->content
)
);
}
}
For the second step you just need to iterate the $temp_array and format as you like

Answer 2

here is another solution to this problem.
$desired_arr = array();
$prev_id = '';
$prev_key = null;
foreach ($orginal_arr as $key => $value) {
$this_id = $value['id'];
if ($this_id == $prev_id) {
array_push($desired_arr[$prev_key][$value['id']], $value['content']);
} else {
$desired_arr[$key][$value['id']] = (array)$value['content'];
$prev_key = $key;
}
$prev_id = $this_id;
}
$desired_arr = array_values($desired_arr);