How can I make this function simpler? Unknown array depth - php

Question

I am back with another question.
I am trying to go through an array and list all the items that match the parent ID of the category and subcategory then list the items in the inventory for the subcategory.
I need to show all items from the category when a button is clicked.
I have a tree view like this
When you click on M8 or 316SS it'll either show the items in M8 or it'll show all the items in the 316SS category.
I need to do this but on every level as well however the code I am currently using doesn't work for it.
Which is this
<?php
include 'classLoader.php';
if (isset($_GET['id']) && !empty($_GET['id'])) {
$items = DB::query("SELECT * FROM inventory WHERE parent=:parent", array(":parent" => $_GET['id']));
if (!empty($items)) {
$data = array();
foreach ($items as $item_key => $item) {
$data["data"][] = array('<i class="icon material-icons">open_in_new</i><a class="link icon-only"><i class="icon material-icons">edit</i></a>', $item['item'], $item['supplier_product_code'], $item['price_per_unit'], $item['current_stock'], $item['category'], '<a class="link icon-only"><i class="icon material-icons">delete</i></a>');
}
header("Content-Type: application/json");
echo json_encode($data, JSON_PRETTY_PRINT);
} else {
$categories = DB::query("SELECT * FROM categories WHERE parent=:id", array(":id" => $_GET['id']));
$data = array();
foreach ($categories as $cat_key => $cat) {
$items = DB::query("SELECT * FROM inventory WHERE parent=:parent", array(":parent" => $cat['id']));
foreach ($items as $item_key => $item) {
$data["data"][] = array('<i class="icon material-icons">open_in_new</i><a class="link icon-only"><i class="icon material-icons">edit</i></a>', $item['item'], $item['supplier_product_code'], $item['price_per_unit'], $item['current_stock'], $item['category'], '<a class="link icon-only"><i class="icon material-icons">delete</i></a>');
}
}
header("Content-Type: application/json");
echo json_encode($data, JSON_PRETTY_PRINT);
}
}
?>
When that didn't work I tried the following code (Cut down but it is pretty much duplicated like 10 times). This code works however it is resource intensive and only goes so many deep. I need one that will continue following it until its got nowhere else to go.
<?php
include 'classLoader.php';
if (isset($_GET['id']) && !empty($_GET['id'])) {
$items = DB::query("SELECT * FROM categories WHERE parent=:id", array(":id" => $_GET['id']));
$d = array();
if (!empty($items)) {
foreach ($items as $item_key => $item) {
$d[] = $item['category_name'];
$subItems = DB::query("SELECT * FROM categories WHERE parent=:catID", array(":catID" => $item['id']));
foreach ($subItems as $item_key => $item) {
$d[] = $item['category_name'];
$subItems = DB::query("SELECT * FROM categories WHERE parent=:catID", array(":catID" => $item['id']));
foreach ($subItems as $item_key => $item) {
$d[] = $item['category_name'];
$subItems = DB::query("SELECT * FROM categories WHERE parent=:catID", array(":catID" => $item['id']));
foreach ($subItems as $item_key => $item) {
$d[] = $item['category_name'];
$subItems = DB::query("SELECT * FROM categories WHERE parent=:catID", array(":catID" => $item['id']));
foreach ($subItems as $item_key => $item) {
$d[] = $item['category_name'];
$subItems = DB::query("SELECT * FROM inventory WHERE parent=:catID", array(":catID" => $item['id']));
}
}
}
}
}
}
header("Content-Type: application/json");
echo json_encode($d, JSON_PRETTY_PRINT);
}
?>
Is there a way to make this function "recursive" in a sense? The database is like this
# categories
| category_name | parent |
| Fasteners | 0 |
| Bolts | 1 |
| 316SS | 2 |
| M8 | 3 |
# inventory
| item | parent |
| 20 | 0 |
| 30 | 1 |
These tables both have over 3000 unique items in them.
Sorry for the very low quality question.

Answer 1

Solved.
I used the following code.
$cats = DB::query("SELECT * FROM categories");
$r = fetch_recursive($cats, $_GET['id']);
foreach ($r as $cat_key => $cat) {
$items = DB::query("SELECT * FROM inventory WHERE parent=:parent", array(":parent" => $cat['id']));
foreach ($items as $item_key => $item) {
$data["data"][] = array('<i class="icon material-icons">open_in_new</i><a class="link icon-only"><i class="icon material-icons">edit</i></a>', $item['item'], $item['supplier_product_code'], $item['price_per_unit'], $item['current_stock'], $item['category'], '<a class="link icon-only"><i class="icon material-icons">delete</i></a>');
}
}
function fetch_recursive($src_arr, $id, $parentfound = false, $cats = array())
{
foreach($src_arr as $row)
{
if((!$parentfound && $row['id'] == $id) || $row['parent'] == $id)
{
$rowdata = array();
foreach($row as $k => $v)
$rowdata[$k] = $v;
$cats[] = $rowdata;
if($row['parent'] == $id)
$cats = array_merge($cats, fetch_recursive($src_arr, $row['id'], true));
}
}
return $cats;
}