```php
<?php
// Database configuration
define('DB_HOST', 'localhost');
define('DB_USER', 'root');
define('DB_PASS', '');
define('DB_NAME', 'cebelarstvo_cigoj');

// Establish database connection
try {
    $pdo = new PDO("mysql:host=".DB_HOST.";dbname=".DB_NAME, DB_USER, DB_PASS);
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
} catch(PDOException $e) {
    die("ERROR: Could not connect. " . $e->getMessage());
}

// Set headers for API
header("Content-Type: application/json; charset=UTF-8");
header("Access-Control-Allow-Origin: *");
header("Access-Control-Allow-Methods: GET, POST, PUT, DELETE");
header("Access-Control-Allow-Headers: Content-Type, Access-Control-Allow-Headers, Authorization, X-Requested-With");

// JWT Secret key
define('JWT_SECRET', 'your_secret_key_here');
?>
```