Recursive Nested Navigation with PHP - php

Question

I know this is asked a lot, but I can't get it to work correctly.
What I have
A PHP function that get's the page id (fk_page).
Inside this function the same function is called to look for child pages.
My Database looks like this:
The PHP Code looks like this:
private function createNav($parent = 0, $sub = false) {
// *!* Create Nav
$getNavPage = $this->model->loadNav($parent); // array of menu items (fk_page) that have $parent as parent.
$NavPage = 0;
foreach ($getNavPage as $getPage) {
$NavPage = intval($getPage["fk_page"]);
$subnav = $this->createNav($NavPage, true); // get childs (recursive loop) and save fk_page in $subnav
if($sub === false) $this->navArr[$parent][] = $NavPage;
else $this->navArr[$parent][][] = $NavPage;
}
return $NavPage;
}
The model does the following
public function loadNav($parent) {
$stmt = $this->pdo->prepare("SELECT fk_page FROM nav WHERE fk_parentpage = " . $parent . ";");
$stmt->execute();
return $stmt->fetchAll();
}
Now the result is an array that looks like this
array(3) {
[0]=>
array(3) {
[0]=>
int(1)
[1]=>
int(2)
[2]=>
int(3)
}
[2]=>
array(1) {
[0]=>
array(1) {
[0]=>
int(4)
}
}
[3]=>
array(2) {
[0]=>
array(1) {
[0]=>
int(5)
}
[1]=>
array(1) {
[0]=>
int(6)
}
}
}
What I would like to have as a result:
array(3) {
[0]=>
array(3) {
[0]=>
int(1)
[1]=>
int(2)
[2]=>
array(1) {
[0]=>
array(1) {
[0]=>
int(4)
}
}
[3]=>
array(2) {
[0]=>
array(1) {
[0]=>
int(5)
}
[1]=>
array(1) {
[0]=>
int(6)
}
}
}
}
I believe that the createNav() must run before the array element is written (or even inside the array $this->NavArr), but I wasn't really succesfull.

Answer 1

Here is an example that uses local data but mimics what you're trying to do:
$data_array = array(
0 => array(1, 2, 3)
, 2 => array(4)
, 3 => array(5, 6)
);
function get_kids($id = 0) {
global $data_array;
if(isset($data_array[$id])) {
return $data_array[$id];
}
else {
return array();
}
}
function create_navigation($parent_id = 0) {
// Check for children
$children_array = get_kids($parent_id);
// No children - just return the parent
if (empty($children_array)) {
return $parent_id;
}
// Children!
foreach ($children_array as $key => $child_id) {
$children_array[$key] = create_navigation($child_id);
}
return array($parent_id => $children_array);
}
echo '<pre>';
$nav = create_navigation(0);
var_dump($nav);
print_r($nav);
echo '</pre>';
The $data_array is used instead of your database.
The get_kids function is your loadNav method.
The create_navigation function is your createNav method.
This produces a var_dump:
array(1) {
[0]=>
array(3) {
[0]=>
int(1)
[1]=>
array(1) {
[2]=>
array(1) {
[0]=>
int(4)
}
}
[2]=>
array(1) {
[3]=>
array(2) {
[0]=>
int(5)
[1]=>
int(6)
}
}
}
}
And a print_r:
Array
(
[0] => Array
(
[0] => 1
[1] => Array
(
[2] => Array
(
[0] => 4
)
)
[2] => Array
(
[3] => Array
(
[0] => 5
[1] => 6
)
)
)
)
The problem with your original code is you were assigning IDs to the class variable $this->navArr instead of using recursion to return the child elements ($subnav).