<?php

$host = 'localhost';
$dbname = 'test';
$charset = 'utf8';

$dbuser = 'root';
$dbpassword = '';

$opt = array(
    PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
    PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC
);

$dsn = "mysql:host = $host; dbname = $dbname; charset = $charset";

$pdo = new PDO($dsn, $dbuser, $dbpassword, $opt);

<?php

function getAllWorkers() {
    $stmt = $pdo->query('SELECT * FROM `workers`');

    while($row = $stmt->fetch()) {
        echo $row['name'];
    }
}

<?php

function getAllWorkers() {
    global $pdo;
    ...

<?php

require_once '../config/config.php';
require_once '../libs/Functions.php';
require_once '../config/db.php';

$controllerName = isset($_GET['controller']) ? ucfirst($_GET['controller']) : 'Index';
$actionName = isset($_GET['action']) ? $_GET['action'] : 'index';

loadPage($twig, $controllerName, $actionName);