Backend\Modules\FormBuilder\Ajax\DeleteField::execute PHP Method

    public function execute()
    {
        parent::execute();
        // get parameters
        $formId = trim(\SpoonFilter::getPostValue('form_id', null, '', 'int'));
        $fieldId = trim(\SpoonFilter::getPostValue('field_id', null, '', 'int'));
        // invalid form id
        if (!BackendFormBuilderModel::exists($formId)) {
            $this->output(self::BAD_REQUEST, null, 'form does not exist');
        } else {
            // invalid fieldId
            if (!BackendFormBuilderModel::existsField($fieldId, $formId)) {
                $this->output(self::BAD_REQUEST, null, 'field does not exist');
            } else {
                // get field
                $field = BackendFormBuilderModel::getField($fieldId);
                // submit button cannot be deleted
                if ($field['type'] == 'submit') {
                    $this->output(self::BAD_REQUEST, null, 'submit button cannot be deleted');
                } else {
                    // delete field
                    BackendFormBuilderModel::deleteField($fieldId);
                    // success output
                    $this->output(self::OK, null, 'field deleted');
                }
            }
        }
    }