What are common pitfalls when using custom autoload functions in PHP, especially in conjunction with third-party libraries like Smarty?

Common pitfalls when using custom autoload functions in PHP, especially with third-party libraries like Smarty, include conflicts with existing autoloaders, incorrect file path resolutions, and inconsistent class naming conventions. To avoid these issues, it's important to properly register the custom autoloader using spl_autoload_register() and ensure that the file paths are correctly mapped to class names.

// Custom autoloader function
function custom_autoloader($class) {
    $class = str_replace('\\', '/', $class);
    $file = __DIR__ . '/path/to/classes/' . $class . '.php';
    
    if (file_exists($file)) {
        require_once $file;
    }
}

// Register custom autoloader
spl_autoload_register('custom_autoloader');