Method addPath

/**
 * Method to add a path to the list of include paths for one of the form's entities.
 * Currently supported entities: field, rule and form. You are free to support your own in a subclass.
 *
 * @param   string  $entity  Form's entity name for which paths will be added.
 * @param   mixed   $new     A path or array of paths to add.
 *
 * @return  array  The list of paths that have been added.
 *
 * @since   1.7.0
 */
protected static function addPath($entity, $new = null)
{
    if (!isset(self::$paths[$entity])) {
        self::$paths[$entity] = [];
    }
    // Reference to an array with paths for current entity
    $paths =& self::$paths[$entity];
    // Force the new path(s) to an array.
    settype($new, 'array');
    // Add the new paths to the stack if not already there.
    foreach ($new as $path) {
        $path = \trim($path);
        if (!\in_array($path, $paths)) {
            \array_unshift($paths, $path);
        }
    }
    return $paths;
}