如何通过考虑表customer_stock中的两个条件来获得数量

I am stuck with a problem in php, mysql and json I am not able to retrieve data from the database by selecting two conditions I have attached a screenshot as well I want to retrieve the quantity from table customer_stock by considering two conditions: customer and name

$line = $db->queryUniqueObject("SELECT * FROM stock_details  WHERE stock_name ='" . $_POST['stock_name1'] . "'");
$cost = $line->company_price;
$sell = $line->selling_price;
$stock_id = $line->stock_id;
$line = $db->queryUniqueObject("SELECT * FROM customer_stock WHERE name='" . $_POST['stock_name1'] . "'");

$stock = $line->quantity;

if ($line != NULL) {

    $arr = array("cost" => "$cost", "sell" => "$sell", "stock" => "$stock", "guid" => $stock_id);
    echo json_encode($arr);

} else {
    $arr1 = array("no" => "no");
    echo json_encode($arr1);
}