Datasource not available within second while loop - php

Question

I have the following php code:
$user_id = $user["id_user_key"];
$stmt = $db->prepare("CALL spGetUserProducts(?)");
$stmt->bind_param('i', $user_id);
$stmt->execute();
$result = $stmt->get_result();
$data = array();
while($row = $result->fetch_assoc()) {
$row_array = array();
$row_array["id"] = $row["id"];
$row_array["pname"] = $row["pname"];
$row_array["picon"] = $row["picon"];
$row_array["menuItems"] = array();
$product = $row["id"];
//loop
$result_opt = $db->query("CALL spGetUserProductViews($user_id, $product)");
while ($opt_fet = $result_opt->fetch_assoc()) {
$row_array["menuItems"][] = array(
"id" => $opt_fet["id"],
"vname" => $opt_fet["vname"],
"isheader" => $opt_fet["isheader"]
);
}
array_push($data, $row_array);
}
$stmt->close();
echo json_encode($data);
The first loop can get a hold of $db, in other words: the first prepared statement is being excecuted and gives me results. The second one:
$result_opt = $db->query("CALL spGetUserProductViews($user_id, $product)");
gives me false. When I try this statement outside the loop, it does work.
Any thoughts ont his?

Answer 1

I found out that mysqli can't handle two simultaneous queries because mysqli uses unbuffered queries by default. Now, I could have dived into this (for example make use of $stmt->store-result()), but I also realized that I would like to keep the load on my database to a minimum.
My solution:
$data = array();
$user_id = $user["id_user_key"];
//menus -> products
$stmt = $db->prepare("CALL spGetUserProducts(?)");
$stmt->bind_param("i", $user_id);
$stmt->execute();
$result = $stmt->get_result();
$menus = array();
while($row = $result->fetch_assoc()) {
$menus[] = $row;
}
$stmt->close();
//items -> views
$stmt = $db->prepare("CALL spGetUserProductViews(?)");
$stmt->bind_param("i", $user_id);
$stmt->execute();
$result = $stmt->get_result();
$items = array();
while($row = $result->fetch_assoc()) {
$items[] = $row;
}
$stmt->close();
//generate object
//loop menus
foreach($menus as $m){
$row_array = array();
$row_array["id"] = $m["id"];
$row_array["pname"] = $m["pname"];
$row_array["picon"] = $m["picon"];
$row_array["menuItems"] = array();
//loop items
foreach($items as $i) {
if($m["id"] == $i["id_product"]) {
$row_array["menuItems"][] = array(
"id" => $i["id"],
"vname" => $i["vname"],
"isheader" => $i["isheader"]
);
}
}
array_push($data, $row_array);
}
echo json_encode($data);
So now I first generate arrays out of the two objects. then I do a foreach over the menus and then over the items. When the $menu["id"] equals $items["id_product"] then the array with items for that specific menu is being generated.
EDIT
After the data has been pulled from the database I first have to do a check wether or not the array contains data:
if(!empty($menus) && !empty($items)) {
foreach ($menus as $m) {
$row_array = array();
$row_array["id"] = $m["id"];
$row_array["pname"] = $m["pname"];
$row_array["picon"] = $m["picon"];
$row_array["menuItems"] = array();
//loop items
foreach ($items as $i) {
if ($m["id"] == $i["id_product"]) {
$row_array["menuItems"][] = array(
"id" => $i["id"],
"vname" => $i["vname"],
"isheader" => $i["isheader"]
);
}
}
array_push($data, $row_array);
}
}