PHP hierarchical array - Parents and childs

Question

I use PHP and mySQL with Idiorm. That might not be relevant.

My PHP array

• It\'s a relationship between parents and childs.
• 0

Answer 1

I had a different problem and could not find a solution that worked for me on this page. I needed to create a tree but without knowing the root id. This means I have to go through my flat array and build branches with the most parently items at the top of the tree.

If anyone else needs to build a tree without a root parent item id, here's how I did it.

 1001,
        'parentid' => 1000,
        'name' => 'test1.1'
    ],
    (object) [
        'id' => 1000,
        'parentid' => 100,
        'name' => 'test1'
    ],
    (object) [
        'id' => 1002,
        'parentid' => 1000,
        'name' => 'test1.2'
    ],
    (object) [
        'id' => 1004,
        'parentid' => 1001,
        'name' => 'test1.1.1'
    ],
    (object) [
        'id' => 1005,
        'parentid' => 1004,
        'name' => 'test1.1.1.1'
    ],
    (object) [
        'id' => 100,
        'parentid' => 10,
        'name' => 'test 0'
    ],
    (object) [
        'id' => 1006,
        'parentid' => 1002,
        'name' => 'test1.2.1'
    ],
    (object) [
        'id' => 1007,
        'parentid' => 1002,
        'name' => 'test1.2.2'
    ],
];

function add_child(stdClass $parent, stdClass $child) {
    if ($child->parentid != $parent->id) {
        throw new Exception('Attempting to add child to wrong parent');
    }

    if (empty($parent->children)) {
        $parent->children = [];
    } else {
        // Deal where already in branch.
        foreach ($parent->children as $idx => $chd) {
            if ($chd->id === $child->id) {
                if (empty($chd->children)) {
                    // Go with $child, since $chd has no children.
                    $parent->children[$idx] = $child;
                    return;
                } else {
                    if (empty($child->children)) {
                        // Already has this child with children.
                        // Nothing to do.
                        return;
                    } else {
                        // Both childs have children - merge them.
                        $chd->children += $child->children;
                        $parent->children[$idx] = $child;
                        return;
                    }
                }
            }
        }
    }

    $parent->children[] = $child;
}

function build_branch(&$branch, &$rows, &$parent = null) {
    $hitbottom = false;
    while (!$hitbottom) {
        $foundsomething = false;
        // Pass 1 - find children.
        $removals = []; // Indexes of rows to remove after this loop.
        foreach ($rows as $idx => $row) {
            if ($row->parentid === $branch->id) {
                // Found a child.
                $foundsomething = true;
                // Recurse - find children of this child.
                build_branch($row, $rows, $branch);
                add_child($branch, $row);
                $removals[] = $idx;
            }
        }
        foreach ($removals as $idx) {
            unset($rows[$idx]);
        }
        // Pass 2 - find parents.
        if ($parent === null) {
            $foundparent = false;
            foreach ($rows as $idx => $row) {
                if ($row->id === $branch->parentid) {
                    // Found parent
                    $foundsomething = true;
                    $foundparent = true;

                    add_child($row, $branch);
                    unset ($rows[$idx]);
                    // Now the branch needs to become the parent since parent contains branch.
                    $branch = $row;
                    // No need to search for other parents of this branch.
                    break;
                }
            }
        }

        $hitbottom = !$foundsomething;
    }
}

function build_tree(array $rows) {
    $tree = [];
    while (!empty($rows)) {
        $row = array_shift($rows);
        build_branch($row, $rows);
        $tree[] = $row;
    }
    return $tree;
}

$tree = build_tree($rows);

print_r($tree);