PHP MySQL building a 3 Tier multi dimensional array - php

Question

So I have my query, its returning results as expect all is swell, except today my designer through in a wrench. Which seems to be throwing me off my game a bit, maybe its cause Im to tired who knows, anyway..
I am to create a 3 tier array
primary category, sub category (which can have multiples per primary), and the item list per sub category which could be 1 to 100 items.
I've tried foreach, while, for loops. All typically starting with $final = array(); then the loop below that.
trying to build arrays like:
$final[$row['primary]][$row['sub']][] = $row['item]
$final[$row['primary]][$row['sub']] = $row['item]
I've tried defining them each as there own array to use array_push() on. And various other tactics and I am failing horribly. I need a fresh minded person to help me out here. From what type of loop would best suit my need to how I can construct my array(s) to build out according to plan.
The Desired outcome would be
array(
primary = array
(
sub = array
(
itemA,
itemB,
itemC
),
sub = array
(
itemA,
itemB,
itemC
),
),
primary = array
(
sub = array
(
itemA,
itemB,
itemC
),
sub = array
(
itemA,
itemB,
itemC
),
),
)

Answer 1

Something like this during treatment of your request :
if (!array_key_exists($row['primary'], $final)) {
$final[$row['primary']] = array();
}
if (!array_key_exists($row['sub'], $final[$row['primary']])) {
$final[$row['primary']][$row['sub']] = array();
}
$final[$row['primary']][$row['sub']][] = $row['item'];

Answer 2

Something like this....
$final =
array(
'Primary1'=>array(
'Sub1'=>array("Item1", "Item2"),
'Sub2'=>array("Item3", "Item4")
),
'Primary2'=>array(
'Sub3'=>array("Item5", "Item6"),
'Sub4'=>array("Item7", "Item8")
),
);
You can do it using array_push but it's not that easy since you really want an associative array and array_push doesn't work well with keys. You could certainly use it to add items to your sub-elements
array_push($final['Primary1']['Sub1'], "Some New Item");

Answer 3

If I understand you correctly, you want to fetch a couple of db relations into an PHP Array.
This is some example code how you can resolve that:
<?php
$output = array();
$i = 0;
// DB Query
while($categories) { // $categories is an db result
$output[$i] = $categories;
$ii = 0;
// DB Query
while($subcategories) { // $subcategories is an db result
$output[$i]['subcategories'][$ii] = $subcategories;
$iii = 0;
// DB Query
while($items) { // $items is an db result
$output[$i]['subcategories'][$ii]['items'][$iii] = $items;
$iii++;
}
$ii++;
}
$i++;
}
print_r($output);
?>