Correct use of PDO procedure not using global - php

Question

I am having a play around with PDO and currently have the following code but I am getting Call to a member function prepare() on a non-object and I don't want to use global.
Do I use a class or do I pass it as a variable?
Config.php
function connection()
{
try
{
$host = 'localhost';
$dbuser = '';
$dbpass = '';
$dbname = '';
$dbConnection = new PDO("mysql:host=" . $host . ";dbname=" . $dbname.";", $dbuser, $dbpass);
return $dbConnection;
} catch (PDOException $error)
{
echo $error->getMessage();
return FALSE;
}
}
Functions.php
<?php
include('config.php');
$db = connection();
function listCars()
{
$query = $db->prepare("SELECT `id` `rego` `engineSize` `type` `colour` `year` `additionalFeatures` FROM `cars`");
$result = $query->fetchAll();
return $result;
}
?>
Index.php
<?php
include('assets/misc/functions.php');
var_dump(listcars());
?>

Answer 1

You have to load the db variable into your function, in Functions.php, look at this:
Functions.php
include('config.php');
$db = connection();
function listCars($db){
$query = $db->prepare("SELECT `id` `rego` `engineSize` `type` `colour` `year` `additionalFeatures` FROM `cars`");
$result = $query->fetchAll();
return $result;
}
?>
Index.php
<?php
include('assets/misc/functions.php');
var_dump(listcars($db));
?>
However, if you're looking for a more OOP approach, try the following:
<?php
class Cars {
protected $db;
public function __construct(PDO $db){
$this->db = $db;
}
public function listCars(){
$query = $this->db->prepare("... query ...")->execute();
return $query->fetchAll();
}
}
include('config.php');
$cars = new Cars(connection());
try {
var_dump($cars->listCars());
} catch (PDOException $e) {
echo $e;
}
?>