Hot to use variable in query in Drupal 8? - drupal-8

Question

I have this code:
function my_module_test($key_make = '') {
$db = new mysqli('xxx', 'xxx', 'xxx', "xxx");
mysqli_set_charset($db, "UTF8");
if ($key_make) {
$sql_model = "SELECT * FROM `car_model` WHERE `id_car_make` = ('$key_make')";
$res_model = $db->query($sql_model) or die(mysqli_error($db));
while ($row = mysqli_fetch_object($res_model)) {
$Key_model = $row->id_car_model;
$Model_value = $row->name;
$dropdown_model[$Key_model] = $Model_value;
}
}
return $dropdown_model;
}
How can I pass the value of the variable $key_make in WHERE clausole ?

Answer 1

The query function takes a second parameter with an array of replacement values, so you would do it like this:
$sql_model = "SELECT * FROM {car_model} WHERE id_car_make = :make";
$res_model = $db->query($sql_model, [':make' => $key_make]);
Static queries are documented here
You could also use a dynamic query (documented here):
$query = $db->select('car_model', 'cm');
$query->fields('cm');
$query->condition('cm.id_car_make', $key_make);
$res_model = $query->execute();
But...
if your "car_model"s are custom entities (which they should be as you will get many benefits like views integration), you should probably use an entityQuery

Answer 2

First you need to use the Drupal Database API to connect to a database. So my final code is the following and it works.
function car2db_model_dropdown_options($key_make) {
$connection = Database::getConnection('default', 'migrate');
$dropdown_model = ['_none'=>'Select'];
$key_make = (int)$key_make;
$sql_model = "SELECT * FROM car_model WHERE id_car_make = :make";
$query = $connection->query($sql_model, [':make' => $key_make]);
$result = $query->fetchAll();
foreach ($result as $row) {
$Key_model = $row->id_car_model;
$Model_value = $row->name;
$dropdown_model[$Key_model] = $Model_value;
}
return $dropdown_model;
}