Get all child, grandchild etc nodes under parent using php with mysql query results

php mysql database tree nodes

20,893

Edit:

I had previously posted a solution to build a multi-dimensional array out of the output you gave as well as a way to get all child elements of a particular id out of that particular array. I have now figured out how to retrieve the child elements straight from your output (without having to first go through a buildtree() function:

function fetch_recursive($src_arr, $currentid, $parentfound = false, $cats = array())
{
    foreach($src_arr as $row)
    {
        if((!$parentfound && $row['id'] == $currentid) || $row['parent_id'] == $currentid)
        {
            $rowdata = array();
            foreach($row as $k => $v)
                $rowdata[$k] = $v;
            $cats[] = $rowdata;
            if($row['parent_id'] == $currentid)
                $cats = array_merge($cats, fetch_recursive($src_arr, $row['id'], true));
        }
    }
    return $cats;
}

To use the function above, simply pass in the output array $data to the first argument and the id you want to retrieve the child elements from in the second argument:

ex.:

$list = fetch_recursive($data, 3);

Which should give you the correct array structure for id 3 (as seen in the example in the last codebox to this answer).

Original Answer:

I had never got around to writing a recursive function to build nested trees out of this design until now. I'm sure there are plenty of others who have written similar functions, but this one should definitely work for you:

function buildtree($src_arr, $parent_id = 0, $tree = array())
{
    foreach($src_arr as $idx => $row)
    {
        if($row['parent_id'] == $parent_id)
        {
            foreach($row as $k => $v)
                $tree[$row['id']][$k] = $v;
            unset($src_arr[$idx]);
            $tree[$row['id']]['children'] = buildtree($src_arr, $row['id']);
        }
    }
    ksort($tree);
    return $tree;
}

This function will recursively build a tree out of an adjacency list and keep the id's ordered in ascending order. This also makes the id's of each parent/child the key of each array of information.

This code:

$r = mysql_query("SELECT * FROM test ");
$data = array();
while($row = mysql_fetch_assoc($r)) {
    $data[] = $row;
}
echo '<pre>';
print_r(buildtree($data));
echo '</pre>';

Will output something like this:

To get all child-nodes of a particular id onto a one-dimensional array, you can use this function:

function fetch_recursive($tree, $parent_id, $parentfound = false, $list = array())
{
    foreach($tree as $k => $v)
    {
        if($parentfound || $k == $parent_id)
        {
            $rowdata = array();
            foreach($v as $field => $value)
                if($field != 'children')
                    $rowdata[$field] = $value;
            $list[] = $rowdata;
            if($v['children'])
                $list = array_merge($list, fetch_recursive($v['children'], $parent_id, true));
        }
        elseif($v['children'])
            $list = array_merge($list, fetch_recursive($v['children'], $parent_id));
    }
    return $list;
}

Based on the buildtree() function above, let's say we wanted to get all child nodes of id 3:

echo '<pre>';
print_r(fetch_recursive(buildtree($a), 3));
echo '</pre>';

This will output:

Array
(
    [0] => Array
        (
            [id] => 3
            [name] => Portable Electronics
            [parent_id] => 1
        )

    [1] => Array
        (
            [id] => 7
            [name] => Mp3 Players
            [parent_id] => 3
        )

    [2] => Array
        (
            [id] => 10
            [name] => Flash
            [parent_id] => 7
        )

    [3] => Array
        (
            [id] => 8
            [name] => CD Players
            [parent_id] => 3
        )

    [4] => Array
        (
            [id] => 9
            [name] => 2 Way Radios
            [parent_id] => 3
        )

)

20,893

Author by

Benny33

Updated on July 16, 2020

Comments

Benny33 almost 4 years

I've been trying to figure this out but I haven't gotten anywhere.Hopefully someone can come to my rescue.

My problem is I'm using adjacency list data model to produce my hierarchy data in mysql.I can retrieve the table (see below) into a multidimension array with associative array for each item. What I want to do is once I get this array , I want to get another array with all the nodes (child, grandchild etc) under a parent id (including the parent item).I just can't workout how to code tihs in php.

In MySQL my table appears like this:

id     name       parent_id
1  Electronics          0
2  Televisions          1
3  Portable Electronics 1
4  Tube                 2
5  LCD                  2
6  Plasma               2
7  Mp3 Players          3
8  CD Players           3
9  2 Way Radios         3
10 Flash                7

I can retrive all rows with this code into an associative array with this.

$r = mysql_query("SELECT * FROM test ");
        $data = array();
        while($row = mysql_fetch_assoc($r)) {
         $data[] = $row;
         }

Gets Results:

Array 
( 
    [0] => Array 
    ( 
        [id] => 1 
        [name] => Electronics 
        [parent_id] => 0 
    ) 
    [1] => Array 
    ( 
        [id] => 2 
        [name] => Televisions 
        [parent_id] => 1 
    ) 
    [2] => Array 
    ( 
        [id] => 3 
        [name] => Portable Electronics 
        [parent_id] => 1 
    )
    [3] => Array 
    (
        [id] => 4 
        [name] => Tube 
        [parent_id] => 2 
    )
    [4] => Array 
    (
        [id] => 5 
        [name] => LCD 
        [parent_id] => 2
    )
    [5] => Array
    (
        [id] => 6 
        [name] => Plasma 
        [parent_id] => 2
    )
    [6] => Array
    (
        [id] => 7 
        [name] => Mp3 Players 
        [parent_id] => 3 
    )
    [7] => Array 
    (
        [id] => 8 
        [name] => CD Players 
        [parent_id] => 3
    )
    [8] => Array 
    (
        [id] => 9 
        [name] => 2 Way Radios 
        [parent_id] => 3
    )
    [9] => Array
    (
        [id] => 10 
        [name] => Flash 
        [parent_id] => 7 
    ) 
)

With those result I want to filter it down with an id.

Say for example I wanted an associative array of every node under Portable Electronics with the id of 3.(Use id for code)

It would return an array with rows with ids:

3 Portable Electronics (Selected parent has to be included)
7 Mp3 Players (Child)
8 CD Players (Child)
9 2 way Radios (Child)
10 Flash (Grand Child)

if Flash had children it would return those as well.

So the end result would return an array like the one above however only with those items.

Please note: I'm not after a function that creates a multidimension array of the tree structure (Already got a solution for that) .I want to build a function: fetch_recursive($id) which receives an ID and returns all the items in that level and in the levels below etc etc.

Hope this helps

Thanks in advance

Benny33 almost 12 years

Thank you so much , exactly what I wanted.Some of the other code you posted here would have been very helpful to me a few days ago, anyway I'm sure it will come in handy for someone else.Again thank you for your detailed response.Cheers
ankitr about 9 years

this is working fine. But I want to see if fetching recursive children is possible in BFS. If yes, then please post the code.
Vipin Singh over 8 years

Hi Zane can you also explain how to print tree?