If we develop a bit more complex theme or plugin where we want to use the modern PHP concepts, probably we want to use a simple autoloader for that. This snippet provides a starting point how could a basic WordPress compatible loader looks like. Replace the paths and the namespaces and you are ready to go!
// The autoloader takes care of automatic file loading. // If the given class has the namespace we want, and // the file exists we include it automatically. spl_autoload_register(function ($class) { if (strpos($class, 'Your\\Namespace\\') !== 0) { return; } $file = __DIR__ . sprintf('/your/files/%s.php', str_replace(['Your\\Namespace\\', '\\'], ['', '/'], $class)); if (file_exists($file)) { require_once $file; } });