$fieldList = new FieldList( TextField::create('Name', 'Name'), DropdownField::create('Gender', 'Gender')->setSource(['Male', 'Female']), EmailField::create('Email', 'Email'), TextareaField::create('Message', 'Message') ); $newField = TextField::create('Age', 'Age'); $fieldList->insertAfter('Name', $newField); // add the new 'Age' field after the 'Name' fieldIn this example, a new TextField for the user's age is added to the form after the 'Name' field using the insertAfter method. Package/library: SilverStripe CMS (https://github.com/silverstripe/silverstripe-framework/)