PHP - Adding Variables Together Newbie Question...

Hello! I found this code from github. https://github.com/gburtini/Learning-Library-for-PHP and I want to know if its possible to add variables to it and what changes needed to be done to the whole script.
My first guess is the variables are 

$xs

and 

$ys

I want replace them and add two more. The whole code is he

<?php 

    require_once 'function.php';

    function ll_nn_predict($xs, $ys, $row, $k) {
        $distances = ll_nearestNeighbors($xs, $row);
        $distances = array_slice($distances, 0, $k);

        $predictions = array();
        foreach($distances as $neighbor=>$distance) {
            $predictions[$ys[$neighbor]]++;
        }
        asort($predictions);

        return $predictions;
    }

    function ll_nearestNeighbors($xs, $row) {
        $testPoint = $xs[$row];

        $distances = _ll_distances_to_point($xs, $testPoint);
        return $distances;
    }

    function _ll_distances_to_point($xs, $x) {
        $distances = array();
        foreach($xs as $index=>$xi) {
            $distances[$index] = ll_euclidean_distance($xi, $x);
        }
        asort($distances);
        array_shift($distances);
        return $distances;
    }

and the function.php that is required is this:

<?php

    function ll_transpose($rows) {
        $columns = array();
        for($i=0;$i<count($rows);$i++) {
            for($k = 0; $k<count($rows[$i]); $k++) {
                $columns[$k][$i] = $rows[$i][$k];
            }
        }
        return $columns;
    }

    function ll_mean($array) {
        return array_sum($array)/($array);
    }

    function ll_variance($array) {
        $mean = ll_mean($array);

        $sum_difference = 0;
        $n = count($array);

        for($i=0; $i<$n; $i++) {
            $sum_difference += pow(($array[$i] - $mean),2);
        }

        $variance = $sum_difference / $n;
        return $variance;
    }
 
    function ll_euclidean_distance($a, $b) {
        if(count($a) != count($b))
            return false;
        
        $distance = 0;
        for($i=0;$i<count($a);$i++) {
            $distance += pow($a[$i] - $b[$i], 2);
        }

        return sqrt($distance);
    }

 

I just want to know where is the variables in those 2 scripts and add more as I'm not well versed in using PHP. Thank you!

I'm currently looping on an array with this structu

    Categories{
        CategoryName
        CategoryCode
        CategoryDescription

        Products{
            product_info{
                product_code
                product_type{
                    CountNumber
                    ProductDescription
                }
            }
            prices{
            "wholesale":"250",
            "retail":"400"
            }
        }    
    }

I'm looping on the above array at each level, and I've declared an array so that I can put all my needed values into it

    $priceResult = array();

    foreach($prices->categories as $category){ 
        $categoryName = $category->category_name;
        $categoryCode = $category->category_code;
        $categoryDescription = $category->category_desc;

        foreach($category->products as $product){

            foreach($product->product_info as $info){
                $product_code = $info->product_code;
                foreach($info->product_type as $type){
                    $CountNumber = $type->CountNumber;
                    $ProductDescription = $type->ProductDescription;
                }
            }
            foreach ($product->prices as $price => $amount) {
                $price_amount = $amount;
                
            }
        }
    }

The problem I'm having is I don't know how to properly push into that new ```$priceResult``` array so that I can use PHPExcel to put it into a format with a subheader.

The format I would want from the above example would be something like this

        Test Category 1  |  123  |   Category for Testing
        ==================================================
        PRD123 |  12  |  Product for Testing  |  150.00
        PRD112 |  17  |  Product for Testing  |  250.00

        Test Category 2  |  321  |   New Category for Testing
        =====================================================
        PRD189 |  16  |  Product for Testing  |  450.00
        PRD139 |  34  |  Product for Testing  |  350.00

So basically I want to call PHPExcel on my $priceResult array in order to get that format where I can list my category info, and for each product within that category, I'd have a product row. Everything would be grouped by the category main header

        $build = Excel::create($name, function ($excel) use ($priceResult) {

        $excel->setTitle('Test Products');

UPDATE:

SO I'm thinking my desired resulting array would be something like:

    CategoryCode : 123
    CategoryName : TestCategory
    CategoryDescription: For Testing
        Products{
            0{
                Product_code : 123,
                CountNumber : 12,
                ProductDescription: Test Product,
                price_amount : 150.00
            },
            1{
                Product_code : 112,
                CountNumber : 32,
                ProductDescription: Test Product 2,
                price_amount : 250.00
            }
        }

    
That way each category can be a header and all of its products can be rows for each category