PHP - Echo multidimentional array as HTML list

Question

I'm looking to write a function that takes an array of pages/categories (from a flat database result) and echo to a nested page/category <ul> (HTML unordered list) items based on the parent ids. I would like to do this recursively, so that any level of nesting can be done.

+-------+---------------+---------------------------+
|   id  |   parent_id   |           title           |
+-------+---------------+---------------------------+
|   1   |       0       |   Parent Page             |
|   2   |       1       |   Sub Page                |
|   3   |       2       |   Sub Sub Page            |
|   4   |       0       |   Another Parent Page     |
+-------+---------------+---------------------------+

And this is the array I would like to end up with to process in my view files:

Array
(
[0] => Array
    (
        [id] => 1
        [parent_id] => 0
        [title] => Parent Page
        [children] => Array
                    (
                        [0] => Array
                            (
                                [id] => 2
                                [parent_id] => 1
                                [title] => Sub Page
                                [children] => Array
                                            (
                                                [0] => Array
                                                    (
                                                        [id] => 3
                                                        [parent_id] => 1
                                                        [title] => Sub Sub Page
                                                    )
                                            )
                            )
                    )
    )
[1] => Array
    (
        [id] => 4
        [parent_id] => 0
        [title] => Another Parent Page
    )
)

I found this article which is SIMILAR but NOT DUPLICATE to the one I'm posting, which is where I found the below function which could help with the answer.

function buildTree(array $elements, $parentId = 0) {
$branch = array();

foreach ($elements as $element) {
    if ($element->parent_id == $parentId) {
        $children = buildTree($elements, $element->id);
        if ($children) {
            $element->children = $children;
        }
        $branch[] = $element;
    }
}

return $branch;
}

$tree = buildTree($rows);

EDIT:

I want to echo the data in the below structure:

 <ul> <li><a href="#">Parent Page</a> <ul> <li><a href="#">Sub Page</a> <ul> <li><a href="#">Sub Sub Page</a> </ul> </li> </ul> </li> <li><a href="#">Another Parent Page</a> </li> </ul> 

Answer 1

Try this function and change as your requirement:

function buildTree(Array $data, $parent = 0) {
$tree = array();
foreach ($data as $d) {
    if ($d['parent'] == $parent) {
        $children = buildTree($data, $d['id']);
        // set a trivial key
        if (!empty($children)) {
            $d['_children'] = $children;
        }
        $tree[] = $d;
    }
}
return $tree;
}

function printTree($tree, $r = 0, $p = null) { 
foreach ($tree as $i => $t) {
    $dash = ($t['parent'] == 0) ? '' : str_repeat('-', $r) .' '; 
    printf("\t<option value='%d'>%s%s</option>\n", $t['id'], $dash, $t['name']);
    if ($t['parent'] == $p) {
        // reset $r
       $r = 0; 
    }
    if (isset($t['_children'])) {
        printTree($t['_children'],$sel, ++$r, $t['parent']);
    }
}
}
$rows = array('your array');

$tree = buildTree($rows);

print("<select name='selectionParentpage' class='just_textfield' id='selectionParentpage'><option value=''>--Select Page--</option>\n");
printTree($tree);
print("</select>");

Answer 2

Here is what you can do for the view part

function displayRecursive($array){
    echo "<ul>";
        foreach($array as $value){
        echo "<li><a href='#'>".$value['name']."</a>";
            if(isset($value['children']) && !empty($value['children'])){
                displayRecursive($value['children']);
            }
        }
    echo "</ul>";
}

You can use something like this to get the treeview array:

    function recursive($parentId=0){

    $return = array();

    $titles=$this->db->query("
                SELECT      `t1`. * , `t2`.`id` AS `has_children`
                FROM        `titles` `t1`
                LEFT JOIN   `titles` `t2` ON ( `t1`.id = `t2`.`parent_id` )
                WHERE       `t1`.`parent_id` = '$parentId'
                GROUP BY    `t1`.`id` ")->result_array();
    if(!empty($titles)){          
        foreach ($titles as $k=>$title){
            $item = $title;
            if ($title['has_children']>0){
                $item['sub'] = self::recursive($title['id']);
            }
            array_push($return, $item);
        }
    }

    return $return;
}