Convert PHP array to JSON tree - php

Question

I have got a array in this format:
array(
array('id' => 1, 'parent_id' => null, 'name' => 'lorem ipsum'),
array('id' => 2, 'parent_id' => 1, 'name' => 'lorem ipsum1'),
array('id' => 3, 'parent_id' => 1, 'name' => 'lorem ipsum2'),
array('id' => 4, 'parent_id' => 2, 'name' => 'lorem ipsum3'),
array('id' => 5, 'parent_id' => 3, 'name' => 'lorem ipsum4'),
array('id' => 6, 'parent_id' => null, 'name' => 'lorem ipsum5'),
);
I have to convert this array to json object with this style:
var json = {
id: "1",
name: "loreim ipsum",
data: {},
children: [{
id: "2",
name: "lorem ipsum1",
data: {},
children: [{
id: "3",
name: "lorem ipsum2",
data: {},
children: [{
..............
How can i do this? Thanks.

Answer 1

My solution:
$data = array(
array('id' => 1, 'parent_id' => null, 'name' => 'lorem ipsum'),
array('id' => 2, 'parent_id' => 1, 'name' => 'lorem ipsum1'),
array('id' => 3, 'parent_id' => 1, 'name' => 'lorem ipsum2'),
array('id' => 4, 'parent_id' => 2, 'name' => 'lorem ipsum3'),
array('id' => 5, 'parent_id' => 3, 'name' => 'lorem ipsum4'),
array('id' => 6, 'parent_id' => null, 'name' => 'lorem ipsum5'),
);
$itemsByReference = array();
// Build array of item references:
foreach($data as $key => &$item) {
$itemsByReference[$item['id']] = &$item;
// Children array:
$itemsByReference[$item['id']]['children'] = array();
// Empty data class (so that json_encode adds "data: {}" )
$itemsByReference[$item['id']]['data'] = new StdClass();
}
// Set items as children of the relevant parent item.
foreach($data as $key => &$item)
if($item['parent_id'] && isset($itemsByReference[$item['parent_id']]))
$itemsByReference [$item['parent_id']]['children'][] = &$item;
// Remove items that were added to parents elsewhere:
foreach($data as $key => &$item) {
if($item['parent_id'] && isset($itemsByReference[$item['parent_id']]))
unset($data[$key]);
}
// Encode:
$json = json_encode($data);

Answer 2

Here's code to do what you need. It does not need the items to be in parent-children order in the array, but will finish faster if they are.
Please study the comments to understand what the code is doing and why; and if you still have questions, ask them too!
// Assume your array is $data
$root = new stdClass; // this is your root item
$objectMap = array(); // this holds objects indexed by their id
// Since we need to iterate over the array, but there may be no guarantee
// that an item's parent will be always encountered before the item itself,
// we loop as many times as needed, skipping items whose parent we have not
// yet seen. Hopefully we will see it later and be able to process these
// items in the next iteration.
while (!empty($data)) {
// Remember how many items there are when starting the loop
$count = count($data);
// Do the actual work!
foreach ($data as $key => $row) {
$parentId = $row['parent_id'];
if ($parentId === null) {
// We just met the root element
$current = $root;
}
else if (isset($objectMap[$parentId])) {
// We met an element with a parent that we have already seen
$current = new stdClass;
}
else {
// We met an element with an unknown parent; ignore it for now
continue;
}
// Put the current element on the map so that its children will
// be able to find it when we meet them
$objectMap[$row['id']] = $current;
// Add the item to its parent's children array
$objectMap[$parentId]->children[] = $current;
// Set the item's properties
$current->id = $row['id'];
$current->name = $row['name'];
$current->data = new stdClass; // always empty
$current->children = array();
// We successfully processed this, remove it (see why below!)
unset($data[$key]);
}
// OK, we looped over the array once. If the number of items has
// not been reduced at all, it means that the array contains only
// items whose parents do not exist. Instead of looping forever,
// let's just take what we are given and stop here.
if ($count == count($data)) {
break;
}
// If there are still items in $data, we will now iterate again
// in the hope of being able to process them in the next iteration
}
// All set! If $data is not empty now, it means there were items
// with invalid parent_ids to begin with.
$output = json_encode($root);

Answer 3

My take (I know an answer has been accepted, but I worked on this so I'm gonna post id =P)
// Test data
$data = array(
array('id' => 1, 'parent_id' => null, 'name' => 'lorem ipsum'),
array('id' => 2, 'parent_id' => 1, 'name' => 'lorem ipsum1'),
array('id' => 3, 'parent_id' => 1, 'name' => 'lorem ipsum2'),
array('id' => 4, 'parent_id' => 2, 'name' => 'lorem ipsum3'),
array('id' => 5, 'parent_id' => 3, 'name' => 'lorem ipsum4'),
array('id' => 6, 'parent_id' => null, 'name' => 'lorem ipsum5'),
);
// Randomize, because the data may not be in a top-down order
shuffle( $data );
// Parse and inspect the result
$builder = new TreeBuilder( $data );
echo '<pre>', print_r( $builder->getTree() ), '</pre>';
class TreeBuilder
{
protected $leafIndex = array();
protected $tree = array();
protected $stack;
function __construct( $data )
{
$this->stack = $data;
while( count( $this->stack ) )
{
$this->branchify( array_shift( $this->stack ) );
}
}
protected function branchify( &$leaf )
{
// Root-level leaf?
if ( null === $leaf['parent_id'] )
{
$this->addLeaf( $this->tree, $leaf );
}
// Have we found this leaf's parent yet?
else if ( isset( $this->leafIndex[$leaf['parent_id']] ) )
{
$this->addLeaf( $this->leafIndex[$leaf['parent_id']]['children'], $leaf );
} else {
// Nope, put it back on the stack
$this->stack[] = $leaf;
}
}
protected function addLeaf( &$branch, $leaf )
{
// Add the leaf to the branch
$branch[] = array(
'id' => $leaf['id']
, 'name' => $leaf['name']
, 'data' => new stdClass
, 'children' => array()
);
// Store a reference so we can do an O(1) lookup later
$this->leafIndex[$leaf['id']] = &$branch[count($branch)-1];
}
protected function addChild( $branch, $leaf )
{
$this->leafIndex[$leaf['id']] &= $branch['children'][] = $leaf;
}
public function getTree()
{
return $this->tree;
}
}