FineUploader - 返回成功：DELETE请求时为false

Question

我正在处理使用自定义Wordpress脚本删除文件：

if ( ! wp_verify_nonce($_POST['nonce'],'delete_attachment_'.$_POST['attachment_id']) ) {
        $response['success'] = 'false';
        echo json_encode($response);
        exit();

    } else {

        $attach_id = $_POST['attachment_id'];

        if ($attach_id) {
            wp_delete_attachment( $attach_id, true );
            $response['success'] = 'true';
        }
        echo json_encode($response);
    }

我尝试传递成功：false，当删除失败时，但是concole日志中的响应似乎总是：

[FineUploader 4.2.2] Delete request for 'Clipboard02444.jpg' has succeeded. 

如何将success: false传递给DELETE方法？