Recursive Php function not working - php

Question

I am trying to display in a table all the child nodes from an ID passed as a parameter. I used a recursive function in PHP to do that.
The only problem is that it displays only the 1st child and not all of them.
This is the Tree.
The PHP Function:
$data = array();
$index = array();
$albero = array();
$query = $conn->query("SELECT id, insertedby FROM utenti where insertedby is not null ORDER BY id");
$query->data_seek(0);
while ($row = $query->fetch_assoc()) {
$id = $row["id"];
$parent_id = $row["insertedby"] === NULL ? "NULL" : $row["insertedby"];
$data[$id] = $row;
$index[$parent_id][] = $id;
}
function findNodeLevel($parent_id, $level, $idtosearch)
{
global $data, $index;
$parent_id = $parent_id === NULL ? "NULL" : $parent_id;
print_r($data);
if (isset($index[$parent_id])) {
foreach ($index[$parent_id] as $id) {
$current_id = $data[$id]["id"];
if($current_id == $idtosearch) {
$levell = $level + 1;
return $levell;
}
findNodeLevel($_SESSION['id'], $level + 1, $idtosearch);
}
}
}
This is the result:
Result of the function
The array data displayed in the 2nd image is the $data array.
The while loop:
$result = $conn->query("SELECT id, email, tipoutente, fullname, datainserimento FROM utenti WHERE inseritoda = " . $_SESSION['id']);
while($row = mysqli_fetch_array($result)){
echo "<tr class=\"righe\">";
if($row['tipoutente'] == "GRUPPO PRIVATO" || $row['tipoutente'] == "GRUPPO NEGOZI" || $row['tipoutente'] == "GRUPPO ASSOCIAZIONI") {
$livello = findNodeLevel($_SESSION['id'], 0, $row['id']);
echo "<td class=\"gruppi\">$progressivoutenti</td>";
echo "<td class=\"gruppi\">" . $row['id'] . "</td>";
echo "<td class=\"gruppi\">" . $row['fullname'] . "</td>";
echo "<td class=\"gruppi\">" . $row['email'] . "</td>";
echo "<td class=\"gruppi\">" . $row['tipoutente'] . "</td>";
echo "<td class=\"gruppi\">" . $row['datainserimento'] . "</td>";
//echo "<td class=\"gruppi\">" . $row['datadiff'] . "</td>";
echo "<td class=\"gruppi\">" . $livello . "</td>";
} else {
$livello = findNodeLevel($_SESSION['id'], 0, $row['id']);
echo "<td class=\"dati\">$progressivoutenti</td>";
echo "<td class=\"dati\">" . $row['id'] . "</td>";
echo "<td class=\"dati\">" . $row['fullname'] . "</td>";
echo "<td class=\"dati\">" . $row['email'] . "</td>";
echo "<td class=\"dati\">" . $row['tipoutente'] . "</td>";
echo "<td class=\"dati\">" . $row['datainserimento'] . "</td>";
//echo "<td class=\"dati\">" . $row['datadiff'] . "</td>";
echo "<td class=\"dati\">" . $livello . "</td>";
}
$progressivoutenti++;
echo "</tr>";
}
echo "</table>";

Answer 1

Inside the recursive function, when you call it again, aren't you passing the wrong parameter for parent_id ?
function findNodeLevel($parent_id, $level, $idtosearch)
{
global $data, $index;
$parent_id = $parent_id === NULL ? "NULL" : $parent_id;
print_r($data);
if (isset($index[$parent_id])) {
foreach ($index[$parent_id] as $id) {
$current_id = $data[$id]["id"];
if($current_id == $idtosearch) {
$levell = $level + 1;
return $levell;
}
findNodeLevel($current_id, $level + 1, $idtosearch);
}
}
}