Method getFieldsets

/**
 * Method to get an array of fieldset objects optionally filtered over a given field group.
 *
 * @param   string  $group  The dot-separated form group path on which to filter the fieldsets.
 *
 * @return  array  The array of fieldset objects.
 *
 * @since   1.7.0
 */
public function getFieldsets($group = null)
{
    $fieldsets = [];
    $sets = [];
    // Make sure there is a valid Form XML document.
    if (!$this->xml instanceof \SimpleXMLElement) {
        throw new \UnexpectedValueException(sprintf('%s::%s `xml` is not an instance of SimpleXMLElement', \get_class($this), __METHOD__));
    }
    if ($group) {
        // Get the fields elements for a given group.
        $elements =& $this->findGroup($group);
        foreach ($elements as &$element) {
            // Get an array of <fieldset /> elements and fieldset attributes within the fields element.
            if ($tmp = $element->xpath('descendant::fieldset[@name] | descendant::field[@fieldset]/@fieldset')) {
                $sets = array_merge($sets, (array) $tmp);
            }
        }
    } else {
        // Get an array of <fieldset /> elements and fieldset attributes.
        $sets = $this->xml->xpath('//fieldset[@name and not(ancestor::field/form/*)] | //field[@fieldset and not(ancestor::field/form/*)]/@fieldset');
    }
    // If no fieldsets are found return empty.
    if (empty($sets)) {
        return $fieldsets;
    }
    // Process each found fieldset.
    foreach ($sets as $set) {
        if ((string) $set['hidden'] === 'true') {
            continue;
        }
        // Are we dealing with a fieldset element?
        if ((string) $set['name']) {
            // Only create it if it doesn't already exist.
            if (empty($fieldsets[(string) $set['name']])) {
                // Build the fieldset object.
                $fieldset = (object) array('name' => '', 'label' => '', 'description' => '');
                foreach ($set->attributes() as $name => $value) {
                    $fieldset->{$name} = (string) $value;
                }
                // Add the fieldset object to the list.
                $fieldsets[$fieldset->name] = $fieldset;
            }
        } else {
            // Only create it if it doesn't already exist.
            if (empty($fieldsets[(string) $set])) {
                // Attempt to get the fieldset element for data (throughout the entire form document).
                $tmp = $this->xml->xpath('//fieldset[@name="' . (string) $set . '"]');
                // If no element was found, build a very simple fieldset object.
                if (empty($tmp)) {
                    $fieldset = (object) array('name' => (string) $set, 'label' => '', 'description' => '');
                } else {
                    $fieldset = (object) array('name' => '', 'label' => '', 'description' => '');
                    foreach ($tmp[0]->attributes() as $name => $value) {
                        $fieldset->{$name} = (string) $value;
                    }
                }
                // Add the fieldset object to the list.
                $fieldsets[$fieldset->name] = $fieldset;
            }
        }
    }
    return $fieldsets;
}