Slack Block Kit for PHP

By Jeremy Lindblom (@jeremeamia)

---

Introduction

From Slack's Block Kit documentation:

Block Kit is a UI framework for Slack apps that offers a balance of control and flexibility when building experiences in messages and other surfaces.

Customize the order and appearance of information and guide users through your app's capabilities by composing, updating, sequencing, and stacking blocks — reusable components that work almost everywhere in Slack.

This library provides an OOP interface in PHP for composing messages using Slack Block Kit.

Block Kit Concepts

This library helps you build Slack messages programmatically and dynamically in your code, but you need to know how they work generally first. The library does try to prevent you from doing things you are not permitted to do in Block Kit, but it does not validate or guard against every single rule.

You may want to review the following concepts in the Slack documentation:

• Surfaces – There are 3 types: Message, Modal, and App Home
• Blocks – Includes section, context, actions, and more
• Interactive Components – We call these "Inputs" in this library
• Composition Objects – We call these "Partials" ion the library

In general, we refer to all of the different things in Block Kit collectively as "elements".

Installation

Install easily via Composer:

composer require jeremeamia/slack-block-kit

Then include the Composer-generated autoloader in your project's initialization code.

Note: This library is built for PHP 7.2+.

Basic Usage

This library supports an intuitive syntax for composing Slack messages. The Slack class acts as a façade to the entire library, and let's you start new messages.

<?php

use Jeremeamia\Slack\BlockKit\Slack;

// ...

$msg = Slack::newMessage();
$msg->text('Don\'t you just love XKCD?');
$msg->divider();
$msg->newImage()
    ->title('Team Chat')
    ->url('https://imgs.xkcd.com/comics/team_chat.png')
    ->altText('Comic about the stubbornness of some people switching chat clients');

// Messages can be converted to JSON using PHP's regular `json_encode` function.
$json = json_encode($msg);

Renderers

This library comes with 3 message/surface renderers out of the box.

All the renderers can be accessed from the Slack façade class, as well.

All the examples below will show the message above being rendered.

JSON

This renderer outputs JSON and is similar to just json_encode-ing the message. However, it will use the pretty-print option.

echo Slack::newRenderer()->forJson()->render($msg);

Output

{
    "response_type": "ephemeral",
    "blocks": [
        {
            "type": "section",
            "text": {
                "type": "mrkdwn",
                "text": "Don't you just love XKCD?"
            }
        },
        {
            "type": "divider"
        },
        {
            "type": "image",
            "title": {
                "type": "plain_text",
                "text": "Team Chat",
                "emoji": true
            },
            "image_url": "https:\/\/imgs.xkcd.com\/comics\/team_chat.png",
            "alt_text": "Comic about the stubbornness of some people switching chat clients"
        }
    ]
}

Block Kit Builder

Slack provides an interactive Block Kit Builder for composing/testing messages. This is a great way to play around with and learn the Block Kit format.

The KitBuilder renderer allows you to render your message/surface as a Block Kit Builder link, so you can preview your message in the browser as Slack would render it via their interactive tool.

echo Slack::newRenderer()->forKitBuilder()->render($msg);

Output

https://api.slack.com/tools/block-kit-builder?mode=message&blocks=%5B%7B%22type%22%3A%22section%22%2C%22text%22%3A%7B%22type%22%3A%22mrkdwn%22%2C%22text%22%3A%22Don%27t%20you%20just%20love%20XKCD%3F%22%7D%7D%2C%7B%22type%22%3A%22divider%22%7D%2C%7B%22type%22%3A%22image%22%2C%22title%22%3A%7B%22type%22%3A%22plain_text%22%2C%22text%22%3A%22Team%20Chat%22%2C%22emoji%22%3Atrue%7D%2C%22image_url%22%3A%22https%3A%2F%2Fimgs.xkcd.com%2Fcomics%2Fteam_chat.png%22%2C%22alt_text%22%3A%22Comic%20about%20the%20stubbornness%20of%20some%20people%20switching%20chat%20clients%22%7D%5D

And here's the actual Block Kit Builder link.

It will show up in the Block Kit Builder looking something like this:

CLI

Sometimes previewing the content of a message in the Terminal/CLI is useful, but the JSON representation can be difficult to read. The CLI renderer will render to a more CLI-friendly format.

echo Slack::newRenderer()->forCli()->render($msg);

Output

(•) Only visible to you
message:
  blocks:
    section:
      text:
        mrkdwn: "Don't you just love XKCD?"
    ----------------------------------------
    image:
      title:
        plain_text: "Team Chat"
      image_url: https://imgs.xkcd.com/comics/team_chat.png
      alt_text: Comic about the stubbornness of some people switching chat clients

Supported Elements

The following are supported elements from the Block Kit documentation:

Type	Element	Supported?
Surface	App Home	✅
Surface	Message	✅
Surface	Model	✅
Block	Actions	✅
Block	Checkboxes	❌
Block	Context	✅
Block	Divider	✅
Block	File	❌
Block	Image	✅
Block	Input	✅
Block	Section	✅
Input	Button	✅️
Input	Date Picker	✅
Input	Multi-select Menus	✅✅✅✅✅
Input	Overflow Menu	❌
Input	Plain Text Input	✅
Input	Radio Buttons	❌
Input	Select Menus	✅✅✅✅✅
Partial	Confirm Dialog	✅
Partial	Mrkdwn Text	✅
Partial	Fields	✅
Partial	Option	✅
Partial	Option Group	✅
Partial	Plain Text	✅

Virtual Elements

The following are virtual/custom elements composed of one or more blocks:

• TwoColumnTable - Uses Sections with Fields to create a two-column table with an optional header.

Class Structure

Surfaces and Renderers

The Slack façade provides ways to create surfaces and renderers. A renderer is used to render a surface (and its blocks) into a displayable format.

See the YUML

[Slack]-creates>[Renderer]
[Slack]-creates>[Surface]
[Surface]^[Message]
[Surface]^[Modal]
[Surface]^[AppHome]
[Element]^[Surface]
[Element]^[Block]
[Renderer]^[Json]
[Renderer]^[KitBuilder]
[Renderer]^[Cli]
[Surface]<>->[Block]

Blocks and Other Elements

Blocks are the primary element of the Block Kit. Blocks contain other elements that are grouped into inputs (interactive elements) and partials (repeatable element parts that are not uniquely identifiable).

See the YUML

[Element]^[Surface]
[Element]^[Block]
[Element]^[Input]
[Element]^[Partial]
[Surface]<>->[Block]
[Block]<>->[Input]
[Block]<>->[Partial]
[Input]-[note: examples:;Button;DatePicker{bg:cornsilk}]
[Partial]-[note: examples:;Text;Fields{bg:cornsilk}]
[Block]-[note: examples:;Section;Actions{bg:cornsilk}]

Contributions

Contributions welcome to support new elements, write tests, setup github actions, etc. See the Project tab.

When implementing elements, to fit within the existing DSL, consider these points:

• To set instantiated sub-element objects, provide a set-prefixed setter (e.g., setText(Text $text): self).
  • Should return self to support chaining.
  • Should set the parent (e.g., setParent()) of the sub-element to $this.
• To set simple sub-element objects, provide a simple setter method (e.g., title(string $title): self).
  • Should be in addition to the set-prefixed setter.
  • Should be named after the property being set.
  • Should return self to support chaining.
  • Should have a maximum of 2 parameters.
  • Should call the regular setter (e.g., return $this->setText(new PlainText($title));).
• To set other non-element properties, provide a simple setter method (e.g., url(string $url): self).
  • Should be named after the property being set.
  • Should return self to support chaining.
• To create new sub-elements attached to the current one, provide a new-prefixed factory method (e.g., newImage(): Image).
  • Should return an instance of the sub-element.
  • Should set the parent (e.g., setParent()) of the sub-element to $this before returning.
  • Should support a $blockId parameter if it's a Block or an $actionId parameter if it's an Input element.
• All element types should be defined in the Type class and registered in relevant constant lists to be appropriately validated.
• If you implement a custom constructor for an element, make sure all the parameters are optional.