Slack API - 附件未显示

Question

我为Slack创建了一个（相当简单的）实现，用PHP在一个通道中发布某些消息。一切都很好，除了附件。出于某种原因，他们确实出现在＆＃34;一些＆＃34;消息，但不是一切。

我使用的代码段几乎与此here

相同

<?php
/**
 * Slack Incoming Webhook - Single PHP File
 *
 * @author      Chris - http://codepad.co/cheers | https://github.com/webremote
 * @copyright   Copyright (c) 2016
 * @version     0.0.28
 * @build       20160204
 */
// Settings
$token      = 'xxx-xxx-xxx-xxx-xxx'; // Request your token via https://api.slack.com/tokens
$channel    = '#mandrill-log';

if ($_SERVER['REQUEST_METHOD'] == 'POST') {
    if (!empty($_POST['mandrill_events'])) {
        foreach (json_decode($_POST['mandrill_events'], true) as $entry) {
            // Default values
            $attachments = [];
            $type = 'Unknown';
            $emoji = 'question';
            $text = print_r($entry, true);
            switch ($entry['event']) {
                case 'send':
                    $text = 'Sent a mail to ' . $entry['msg']['email'] . ' with subject "' . $entry['msg']['subject'] . '" (from: ' . $entry['msg']['sender'] . ')';
                    $emoji = 'email';
                    $type = 'Sent';
                    break;

                case 'click':
                    $text = 'Somebody from ' . $entry['location']['country'] . ' clicked the URL "' . $entry['url'] . '"';
                    $emoji = 'point_right';
                    $type = 'Click';
                    $attachments = [
                        'fallback'  => $text,
                        'text'      => 'URL clicked: ' . $entry['url'],
                        'fields'    => [
                            [
                                'title' => 'Location',
                                'value' => $entry['location']['country'] . (!empty($entry['location']['region']) ? PHP_EOL . $entry['location']['region'] : '') . (!empty($entry['location']['city']) ? PHP_EOL . $entry['location']['city'] : ''),
                                'short' => true,
                            ],
                            [
                                'title' => 'Browser',
                                'value' => $entry['user_agent_parsed']['type'],
                                'short' => true
                            ],
                            [
                                'title' => 'Subject',
                                'value' => $entry['msg']['subject'],
                                'short' => true,
                            ],
                            [
                                'title' => 'Sender',
                                'value' => $entry['msg']['sender'],
                                'short' => true
                            ]
                        ],
                        'thumb_url' => $entry['user_agent_parsed']['ua_icon']
                    ];
                    break;

                case 'open':
                    $text = 'Somebody from ' . $entry['location']['country'] . ' opened an email "' . $entry['msg']['subject'] . '"';
                    $emoji = 'open_book';
                    $type = 'Read';
                    $attachments = [[
                        'fallback'  => $text,
                        'fields'    => [
                            [
                                'title' => 'Location',
                                'value' => $entry['location']['country'] . (!empty($entry['location']['region']) ? PHP_EOL . $entry['location']['region'] : '') . (!empty($entry['location']['city']) ? PHP_EOL . $entry['location']['city'] : ''),
                                'short' => true,
                            ],
                            [
                                'title' => 'Browser',
                                'value' => $entry['user_agent_parsed']['type'] . ($entry['user_agent_parsed']['mobile'] ? ' - Mobile' : ' - Desktop'),
                                'short' => true
                            ],
                            [
                                'title' => 'Subject',
                                'value' => $entry['msg']['subject'],
                                'short' => true,
                            ],
                            [
                                'title' => 'Sender',
                                'value' => $entry['msg']['sender'],
                                'short' => true
                            ]
                        ],
                        'thumb_url' => $entry['user_agent_parsed']['ua_icon']
                    ]];
                    break;

                case 'soft_bounce':
                    $text = 'Email to ' . $entry['msg']['email'] . ' with subject "' . $entry['msg']['subject'] . '" got (soft) bounced';
                    $emoji = 'space_invader';
                    $type = 'Bounce';
                    break;

                case 'hard_bounce':
                    $text = 'Email to ' . $entry['msg']['email'] . ' with subject "' . $entry['msg']['subject'] . '" got (hard) bounced (' . $entry['msg']['diag'] .')';
                    $emoji = 'skull_and_crossbones';
                    $type = 'Bounce';
                    break;
            }

            if ($entry['type'] == 'blacklist') {
                if ($entry['action'] == 'add') {
                    $type = 'Blacklist';
                    $emoji = 'new_moon_with_face';
                    $text = 'The e-mail ' . $entry['reject']['email'] . ' has been added to the blacklist (Reason: ' . $entry['reject']['reason'] . ', expires at ' . $entry['reject']['expires_at'] . ')';
                }
            }

            if (empty($attachments)) {
                $ch = curl_init();
                curl_setopt($ch, CURLOPT_USERAGENT,         'Webremote.Mandrill.Webhook');
                curl_setopt($ch, CURLOPT_POST,              true);
                curl_setopt($ch, CURLOPT_URL,               'https://slack.com/api/chat.postMessage?');
                curl_setopt($ch, CURLOPT_POSTFIELDS, [
                    'token'         => $token,
                    'channel'       => $channel,
                    'username'      => 'Mandrill-' . $type,
                    'text'          => $text,
                    'icon_emoji'    => ':' . $emoji . ':'
                ]);
                curl_exec($ch);
                curl_close($ch);
            } 
            elseif (!empty($attachments)) {
                $ch = curl_init();
                curl_setopt($ch, CURLOPT_USERAGENT,         'Webremote.Mandrill.Webhook');
                curl_setopt($ch, CURLOPT_POST,              false);
                curl_setopt($ch, CURLOPT_URL,               'https://slack.com/api/chat.postMessage?' . http_build_query([
                    'token'         => $token,
                    'channel'       => $channel,
                    'username'      => 'Mandrill-' . $type,
                    'text'          => $text,
                    'attachments'   => json_encode($attachments),
                    'icon_emoji'    => ':' . $emoji . ':'
                ]));
                curl_setopt($ch, CURLOPT_RETURNTRANSFER,    1);
                curl_setopt($ch, CURLOPT_HTTPHEADER,        [
                    'content-length: ' . strlen($dataSend)
                ]);
                $response = curl_exec($ch);
                curl_close($ch);               
            }
        }
    }
}

对于＆＃34;案例：发送＆＃34; （第23行）我也想显示附件，但由于某种原因，它不起作用。松弛的结果只是＆＃34; text＆＃34; -field，而附件完全被忽略......没有充分的理由？

我已尝试搜索API文档，常见问题解答甚至是SO，但没有出现任何主题。是否存在附件无法显示的具体原因？