How to group an array into subarrays using its keys? - php

Question

I am looking to group an array into subarrays based on its keys.
Sample Array
Array
(
[0] => Array
(
[a_id] => 1
[a_name] => A1
[b_id] => 1
[b_name] => B1
[c_id] => 1
[c_name] => C1
)
[1] => Array
(
[a_id] => 1
[a_name] => A1
[b_id] => 1
[b_name] => B1
[c_id] => 2
[c_name] => C2
)
[2] => Array
(
[a_id] => 1
[a_name] => A1
[b_id] => 2
[b_name] => B2
[c_id] => 3
[c_name] => C3
)
[3] => Array
(
[a_id] => 2
[a_name] => A2
[b_id] => 3
[b_name] => B3
[c_id] => 4
[c_name] => C4
)
)
I need this sample array to be converted into a JSON array of the following format:
Expected Output
[{
"a_id": 1,
"a_name": "A1",
"b_list": [{
"b_id": 1,
"b_name": "B1",
"c_list": [{
"c_id": 1,
"c_name": "C1"
}, {
"c_id": 2,
"c_name": "C2"
}]
}, {
"b_id": 2,
"b_name": "B2",
"c_list": [{
"c_id": 3,
"c_name": "C3"
}]
}]
}, {
"a_id": 2,
"a_name": "A2",
"b_list": [{
"b_id": 3,
"b_name": "B3",
"c_list": [{
"c_id": 4,
"c_name": "C4"
}]
}]
}]
I was able to group by a key using the code below.
$array = array(
array("a_id" => "1","a_name" => "A1","b_id" => "1","b_name" => "B1","c_id" => "1","c_name" => "C1"),
array("a_id" => "1","a_name" => "A1","b_id" => "1","b_name" => "B1","c_id" => "2","c_name" => "C2"),
array("a_id" => "1","a_name" => "A1","b_id" => "2","b_name" => "B2","c_id" => "3","c_name" => "C3"),
array("a_id" => "2","a_name" => "A2","b_id" => "3","b_name" => "B3","c_id" => "4","c_name" => "C4")
);
$return = array();
foreach($array as $val) {
$return[$val["a_id"]][] = $val;
}
print_r($return);
But my actual scenario involves grouping into sub arrays didn't worked.
Looking forward to see if there is an optimized way or useful function to get into my expected JSON response.
Note: I am looking into a generalized use case here . For example : a_list as countries,b_list as states and c_list as cities.

Answer 1

Man that is very specific use case for arrays. Well here is your solution.
$array = <YOUR SAMPLE ARRAY>
$output = [];
/*
* Nesting array based on a_id, b_id
*/
foreach ($array as $item) {
$aid = $item['a_id'];
$bid = $item['b_id'];
$cid = $item['c_id'];
if(!isset($output[$aid])){
$output[$aid] = [
'a_id' => $item['a_id'],
'a_name' => $item['a_name'],
'b_list' => [
$bid => [
'b_id' => $item['b_id'],
'b_name' => $item['b_name'],
'c_list' => [
$cid = [
'c_id' => $item['c_id'],
'c_name' => $item['c_name']
]
]
]
]
];
} else if (!isset($output[$aid]['b_list'][$bid])){
$output[$aid]['b_list'][$bid] = [
'b_id' => $item['b_id'],
'b_name' => $item['b_name'],
'c_list' => [
$cid => [
'c_id' => $item['c_id'],
'c_name' => $item['c_name']
]
]
];
} else if(!isset($output[$aid]['b_list'][$bid]['c_list'][$cid])) {
$output[$aid]['b_list'][$bid]['c_list'][$cid] = [
'c_id' => $item['c_id'],
'c_name' => $item['c_name']
];
} else {
// Do/Dont overrider
}
}
/*
* Removing the associativity from the b_list and c_list
*/
function indexed($input){
$output = [];
foreach ($input as $key => $item) {
if(is_array($item)){
if($key == 'b_list' || $key == 'c_list'){
$output[$key] = indexed($item);
} else {
$output[] = indexed($item);
}
} else {
$output[$key] = $item;
}
}
return $output;
}
$indexed = indexed($output);
print_r(json_encode($indexed, 128));

Answer 2

Interesting requirement there.
Here is my generalized solution that is also extendable.
function transform($array, $group=[
['a_id','a_name','b_list'],
['b_id','b_name','c_list'],
['c_id','c_name'],
]){
foreach($array as $a){
$r = &$result;
foreach($group as $g){
$x = &$r[$a[$g[0]]];
$x[$g[0]] = $a[$g[0]];
$x[$g[1]] = $a[$g[1]];
if(isset($g[2])) $r = &$x[$g[2]]; else break;
}
}
return transformResult($result);
}
function transformResult($result){
foreach($result as &$a)
foreach($a as &$b)
if(is_array($b)) $b = transformResult($b);
return array_values($result);
}
To extend this solution, all you have to do is modify the $group parameter,
either directly in the function declaration or by passing an appropriate value as the 2nd parameter.
Usage example:
echo json_encode(transform($array), JSON_PRETTY_PRINT);
This will return the same output assuming the same $array input in your example.

Answer 3

Now here is the code that works best in the given situation. I have created a similar situation and then explained the solution in detail.
Situation
The Order Form is multipage depending on the number of days served based on the package selected. Details of each package are stored in the database with the following fields:
package_id (Unique Field)
package_name (Name of the Package, e.g. Package A)
servings_count (Total Servings in a Day)
days_served (Number of Days Served in a Month)
In order to carry forward the selection of meals for each day and serving of that day to store as an Order in the database, I required a Multidimensional Array of PHP that can be defined/populated dynamically.
Expected output is something like:
Array
(
[Day 1] => Array
(
[meal_id_1] => Unique ID //to be replaced with user selection
[meal_code_1] => Meal Name //to be replaced with user selection
[meal_type_1] => Meal //prefilled based on the selected package
[meal_id_2] => Not Available //to be replaced with user selection
[meal_code_2] => 2 //to be replaced with user selection
[meal_type_2] => Meal //prefilled based on the selected package
)
[Day 2] => Array
(
[meal_id_1] => Unique ID //to be replaced with user selection
[meal_code_1] => Meal Name //to be replaced with user selection
[meal_type_1] => Meal //prefilled based on the selected package
[meal_id_2] => Not Available //to be replaced with user selection
[meal_code_2] => 2 //to be replaced with user selection
[meal_type_2] => Meal //prefilled based on the selected package
)
This above array has been created 100% dynamically based on the explained structure and number of servings and days. Below is the code with some explanation.
First, we have to declare two PHP Arrays.
$total_meals_array = []; //Primary, Multidimension Array
$meals_selected_array = []; //Meals Details Array to be used as primary array's key value.
After doing this, run MySQL query to read packages from the database. Now based on the result, do the following:
$total_meals_array = []; //Primary, Multidimension Array
$meals_selected_array = []; //Meals Details Array to be used as primary array's key value.
if( $num_row_packages >= 1 ) {
while($row_packages = mysqli_fetch_array ($result_packages)) {
$package_id = $row_packages['package_id'];
$package_name = $row_packages['package_name'];
$servings_count = $row_packages['servings_count'];
$days_served = $row_packages['days_served'];
//this for loop is to repeat the code inside `$days_served` number of times. This will be defining our primary and main Multidimensional Array `$total_meals_array`.
for ($y = 1; $y <= $days_served; $y++) {
//once inside the code, now is the time to define/populate our secondary array that will be used as primary array's key value. `$i`, which is the meal count of each day, will be added to the key name to make it easier to read it later. This will be repeated `$meals_count` times.
for ($i = 1; $i <= $meals_count; $i++) {
$meals_selected_array["meal_id_" . $i] = "Unique ID";
$meals_selected_array["meal_code_" . $i] = "Meal Name";
$meals_selected_array["meal_type_" . $i] = "Meal";
}
//once our secondary array, which will be used as the primary array's key value, is ready, we will start defining/populating our Primary Multidimensional Array with Keys Named based on `$days_served`.
$total_meals_array["Day " . $y] = $meals_selected_array;
}
}
}
That's it! Our dynamic Multidimensional Array is ready and can be viewed by simply the below code:
print "<pre>";
print_r($total_meals_array);
print "</pre>";
Thank you everyone, specially #yarwest for being kind enough to answer my question.

Answer 4

Here is the code, you can use it for index from a_ to y_ deep. The innerest element is null, if you don't want it. Terminate the for loop before last element, then process last element seperately. You also can do some improvement on this code. Hope this helps.
<?php
$array = array(
array("a_id" => "1","a_name" => "A1","b_id" => "1","b_name" => "B1","c_id" => "1","c_name" => "C1"),
array("a_id" => "1","a_name" => "A1","b_id" => "1","b_name" => "B1","c_id" => "2","c_name" => "C2"),
array("a_id" => "1","a_name" => "A1","b_id" => "2","b_name" => "B2","c_id" => "3","c_name" => "C3"),
array("a_id" => "2","a_name" => "A2","b_id" => "3","b_name" => "B3","c_id" => "4","c_name" => "C4")
);
$arrays = array_map(function($v){return array_chunk($v, 2, true);}, $array);
$result = [];
foreach($arrays as $value)
{
$ref = &$result;
$len = count($value);
$index = 0;
for(; $index < $len; $index++)
{
$arr = $value[$index];
$char = key($arr)[0];
$charAdd = chr(ord($char)+1);
$key = $arr[$char.'_id'].$arr[$char.'_name'];
$listKey = $charAdd.'_list';
foreach($arr as $k => $v)
{
$ref[$key][$k] = $v;
}
$ref = &$ref[$key][$listKey];
}
}
var_dump($result);
Output: the online live demo
ei#localhost:~$ php test.php
array(2) {
["1A1"]=>
array(3) {
["a_id"]=>
string(1) "1"
["a_name"]=>
string(2) "A1"
["b_list"]=>
array(2) {
["1B1"]=>
array(3) {
["b_id"]=>
string(1) "1"
["b_name"]=>
string(2) "B1"
["c_list"]=>
array(2) {
["1C1"]=>
array(3) {
["c_id"]=>
string(1) "1"
["c_name"]=>
string(2) "C1"
["d_list"]=>
NULL
}
["2C2"]=>
array(3) {
["c_id"]=>
string(1) "2"
["c_name"]=>
string(2) "C2"
["d_list"]=>
NULL
}
}
}
["2B2"]=>
array(3) {
["b_id"]=>
string(1) "2"
["b_name"]=>
string(2) "B2"
["c_list"]=>
array(1) {
["3C3"]=>
array(3) {
["c_id"]=>
string(1) "3"
["c_name"]=>
string(2) "C3"
["d_list"]=>
NULL
}
}
}
}
}
["2A2"]=>
array(3) {
["a_id"]=>
string(1) "2"
["a_name"]=>
string(2) "A2"
["b_list"]=>
array(1) {
["3B3"]=>
array(3) {
["b_id"]=>
string(1) "3"
["b_name"]=>
string(2) "B3"
["c_list"]=>
array(1) {
["4C4"]=>
array(3) {
["c_id"]=>
string(1) "4"
["c_name"]=>
string(2) "C4"
["d_list"]=>
&NULL
}
}
}
}
}
}

Answer 5

This is rather interesting. As far as I can tell, you are trying to transform a flat array into a multidimensional array, as well as transforming the keys into a multidimensional representation.
The top level difference seems to reside in the part before the underscore of the a_* keys.
Then, for each of these keys, every other *_ letters should induce it's own list.
This recursive function does the trick without hardcoding, will work with whatever number of levels, letters (or whatever else) and right identifiers.
It seems to return exactly the json you show in the sample ($array being the array as defined in your question)
$multidimension = multidimensionalify($array, ['a', 'b', 'c'], ['name']);
var_dump(json_encode($multidimension, JSON_PRETTY_PRINT));
function multidimensionalify(
array $input,
array $topLevelLetters,
array $rightHandIdentifiers,
$level = 0,
$parentId = null,
$uniqueString = 'id'
)
{
$thisDimension = [];
$thisLetter = $topLevelLetters[$level];
foreach ($input as $entry)
{
$thisId = $entry["{$thisLetter}_{$uniqueString}"];
$condition = true;
if ($parentId !== null)
{
$parentLetter = $topLevelLetters[$level - 1];
$condition = $entry["{$parentLetter}_{$uniqueString}"] === $parentId;
}
if (!isset($thisDimension[$thisId]) && $condition)
{
$thisObject = new stdClass;
$thisObject->{"{$thisLetter}_{$uniqueString}"} = $thisId;
foreach ($rightHandIdentifiers as $identifier)
{
$thisObject->{"{$thisLetter}_{$identifier}"} = $entry["{$thisLetter}_{$identifier}"];
}
if (isset($topLevelLetters[$level + 1])) {
$nextLetter = $topLevelLetters[$level + 1];
$thisObject->{"{$nextLetter}_list"} = multidimensionalify($input, $topLevelLetters, $rightHandIdentifiers, $level + 1, $thisId, $uniqueString);
}
$thisDimension[$thisId] = $thisObject;
}
}
return array_values($thisDimension);
}

Answer 6

Try this function just pass your array and key name for grouping and then convert to json.
public function _group_by($array, $key) {
$return = array();
foreach ($array as $val) {
$return[$val[$key]][] = $val;
}
return $return;
}