php mysql query and array association - php

Question

So I have the next databases:
+------+---------------+-------+
| Id | Title | Price |
+------+---------------+-------+
| 300 | Part1 | 30 |
| 400 | Part2 | 40 |
| 500 | Part3 | 50 |
| 3215 | Promo Package | 130 |
+------+---------------+-------+
And
+-----------------+--------------+
| Promo_prod_main | product_part |
+-----------------+--------------+
| 3215 | 300 |
| 3215 | 400 |
| 3215 | 500 |
+-----------------+--------------+
Those two would create lets say a promo package(the 3 products).
The problem is that sometimes , the prices on the 3 parts change but it won't affect the promo package price.
I decided to create a script that selects each promo package and then gets the products that its created from , sum up the array of the prices and then update the promo package.
All good thinking until I got to code , I managed this far:
$rezultatebumb = mysqli_query($linkul, "SELECT id,title,price FROM product WHERE attr_group_id IS NULL AND is_homepage IS NULL") or die(mysqli_error($linkul)); // this query only selects the promo packages
$array_m = array();
foreach ($rezultatebumb as $valc) {
$array_m[] = $valc['id'];
}
$array_s = array();
foreach ($array_m as $arr) {
$rezprod = mysqli_query($linkul, "SELECT product_part FROM product_promo WHERE Promo_prod_main=" . $arr) or die(mysqli_error($linkul));
$tesat = $rezprod->fetch_assoc();
$array_s[] = $tesat['product_part'];
echo count($array_s);
}
print_r($array_s);
echo '</br></br>';
print_r($array_m);
results next->
One product from each package
Array ( [0] => 146 [1] => 1497 [2] => 565 [3] => 6576 [4] => 1516 )
Each promo package
Array ( [0] => 5732 [1] => 5758 [2] => 6998 [3] => 7032 [4] => 7033 )
Before I get messages like 'You're supposed to write the code yourself' , well I tried, I just can't get anywhere past this point.
I will appreciate any tip or fix to this problem , thank you!.

Answer 1

Sadly the only thing I understand is this part.
I decided to create a script that selects each promo package and then
gets the products that its created from , sum up the array of the
prices and then update the promo package.
So, You can something like joins to get an array of all products which are associated with the promo package.
SELECT p.Price from product p
join promo_table pt
on (p.Id = pt.Promo_prod_main)
where pt.promo_prod_main=3215
Pass it results on array and then do array_sum() to array to get the total of price.
And then update it's total price

Answer 2

you can use inner join to have the package prepared. With query of inner join:
select * from package a
inner join product b
on a.package_id = b.package_id
where a.package_id = 5
Something on these lines, you should have pacakage_id corresponding to each product. Or you can have another mapping table to map a product with various packages.