PDO - Foreach with Array Respect - php

Question

using PDO, I receive 1+ rows and turn them into an array like this:
while($row = $car_sales->fetch(PDO::FETCH_ASSOC)){
$car_id_array[] = $row["car_id"];
$car_type_array[] = $row["car_type"];
$dealer_id_array[] = $row["dealer_id"];
$buyer_id_array[] = $row["seller_id"];
}
I'm trying to simply "mix" each level of the array to act as a unit and go down the foreach loop together, submitting the $q query in order. In other words, something like this:
foreach($dealer_id_array as $dealer_id) {
if ($car_type=='new') {
if ($dealer_id==$buyer_id){
$q = 'UPDATE car_sales SET new_cars=new_cars+1 WHERE dealer_id=:dealer_id';
} else if ($dealer_id!=$buyer_id){
$q = 'UPDATE car_sales SET new_cars=new_cars-1 WHERE dealer_id=:dealer_id';
} else if ($car_type=='old') {
if ($dealer_id==$buyer_id){
$q = 'UPDATE car_sales SET old_cars=old_cars+1 WHERE dealer_id=:dealer_id';
} else if ($dealer_id!=$buyer_id){
$q = 'UPDATE car_sales SET old_cars=old_cars-1 WHERE dealer_id=:dealer_id';
}
$car_update = $dbhandle->prepare($q);
$car_update->execute(array(':dealer_id' => $dealer_id));
}
The loop should run with the first array values if there is only one value retrieved from the while loop. If there are more, the foreach should run as many times as there are dealer_ids from the while loop, while respecting the order. This example won't work, but I'm looking for possible solutions to solve this issue correctly. What do you think would be the most efficient way to do this?

Answer 1

I might be misunderstanding you, but I believe if you just replaced your foreach loop with a for loop, and counted one of the arrays you would solve your issue:
for($i = 0; $i < count($dealer_id_array); $i++) {
and then simply using $i to access the correct item in your arrays:
$car_type_array[$i];
But having said that, I don't really see the point of the initial four arrays in the first place. Could you not just directly execute the code inside the foreach loop straight inside the while loop in the first place?
EDITED: to fix code example