event.create_child.php

<?php
require_once(TOOLKIT . '/class.event.php');

class eventcreate_child extends SectionEvent
{
    public $ROOTELEMENT = 'create-child';
    public $eParamFILTERS = array();

    public static function about()
    {
        return array(
            'name' => 'Create child',
            'author' => array(
                'name' => 'john puddephatt',
                'website' => '###',
                'email' => '###'),
            'version' => 'Symphony 2.6.5',
            'release-date' => '2016-01-29T10:18:14+00:00',
            'trigger-condition' => 'action[create-child]'
        );
    }

    public function priority(){
        return self::kHIGH;
    }

    public static function getSource()
    {
        return '1';
    }

    public static function allowEditorToParse()
    {
        return false;
    }

    public static function documentation()
    {
        return 'Chaining...'                
    }

    public function load()
    {
        $this->post = $_POST;
        if (isset($_POST['action']['create-child'])) {
            unset($_POST['fields']);
            $_POST['fields'] = $this->post['create-child']['fields'];
            $result = $this->__trigger();

            if($result->getAttribute('result') == "success") {
                unset($_POST['action']['create-child']);
                unset($_POST['fields']);
                $_POST['fields'] = $this->post['create-parent']['fields'];
                $child_id = $result->getAttribute('id');
                $_POST['fields']['children']['entries'] = [$child_id];
                $_POST['action']['create-parent'] = 'Submit';                
            }
            return $result;
        }
    }
}