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/modals using Slack Block Kit. It also does the reverse, meaning you can "hydrate" message/modal JSON into an object hierarchy.
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 main 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 slack-php/slack-block-kit
Then include the Composer-generated autoloader in your project's initialization code.
Note: This library is built for PHP 7.3+.
Basic Usage
This library supports an intuitive and fluid syntax for composing Slack surfaces (e.g., messages, modals). The Kit class acts as a façade to the library, and let's you start new messages/modals.
<?php
use SlackPhp\BlockKit\Kit;
use SlackPhp\BlockKit\Surfaces\Message;
// ...
// You can start a message from the `Kit` class.
$msg = Kit::newMessage();
// OR via the surface class's "new" method.
$msg = Message::new();
// Then you can add blocks using the surface's available methods.
$msg->text('Don\'t you just love XKCD?');
$msg->divider();
$msg->newImage()
->title('Team Chat')
->url('https://imgs.xkcd.com/comics/team_chat.png')
->altText('Comic about the stubbornness of some people switching chat clients');
// To convert to JSON (to send to Slack API, webhook, or response_url), use PHP's `json_encode` function.
echo json_encode($msg);
// OR you can use the surfaces's `toJson` method, which also includes a convenience parameter for pretty printing.
echo $msg->toJson(true);
Fluent Interface
When using the fluent interface, every method that sets a property or adds a sub-element returns the original element's object, so you can chain additional method calls.
$msg = Message::new()
->text('Don\'t you just love XKCD?');
->divider();
Methods with a new prefix will return the new element's object, so be careful with how you are using the fluent interface in those cases.
// Correctly renders the whole message.
$msg = Message::new()
->text('Don\'t you just love XKCD?')
->divider();
$msg->newImage()
->title('Team Chat')
->url('https://imgs.xkcd.com/comics/team_chat.png')
->altText('Comic about the stubbornness of some people switching chat clients');
echo json_encode($msg);
// YAY!
// INCORRECT: Renders just the image, because only that element gets stored in the variable.
$msg = Message::new()
->text('Don\'t you just love XKCD?')
->divider()
->newImage()
->title('Team Chat')
->url('https://imgs.xkcd.com/comics/team_chat.png')
->altText('Comic about the stubbornness of some people switching chat clients');
echo json_encode($msg);
// WHOOPS!
Tapping
Tapping is a way to keep the fluent interface going, but makes sure the whole message is preserved.
// Correctly renders the whole message, by using tap()
$msg = Message::new()
->text('Don\'t you just love XKCD?')
->divider()
->tap(function (Message $msg) {
$msg->newImage()
->title('Team Chat')
->url('https://imgs.xkcd.com/comics/team_chat.png')
->altText('Comic about the stubbornness of some people switching chat clients');
});
echo json_encode($msg);
// YAY!
Preview in Block Kit Builder
Slack provides an interactive Block Kit Builder for composing/testing messages and other surfaces. This is a great way to play around with and learn the Block Kit format.
The Kit::preview method allows you to render your message/surface as a Block Kit Builder URL, so you can link to a preview or your message/surface in the browser via their interactive tool. This will help you see how it would be rendered in a Slack client.
$msg = Kit::newMessage()
->text('Don\'t you just love XKCD?')
->divider()
->tap(function (Message $msg) {
$msg->newImage()
->title('Team Chat')
->url('https://imgs.xkcd.com/comics/team_chat.png')
->altText('Comic about the stubbornness of some people switching chat clients');
});
echo Kit::preview($msg);
Output
https://app.slack.com/block-kit-builder#%7B"blocks":%5B%7B"type":"section"%2C"text":%7B"type":"mrkdwn"%2C"text":"Don%27t%20you%20just%20love%20XKCD%3F"%7D%7D%2C%7B"type":"divider"%7D%2C%7B"type":"image"%2C"title":%7B"type":"plain_text"%2C"text":"Team%20Chat"%7D%2C"image_url":"https:%5C%2F%5C%2Fimgs.xkcd.com%5C%2Fcomics%5C%2Fteam_chat.png"%2C"alt_text":"Comic%20about%20the%20stubbornness%20of%20some%20people%20switching%20chat%20clients"%7D%5D%7D
And here's the actual Block Kit Builder link.
It will show up in the Block Kit Builder looking something like this:
Surface Hydration
Some Slack application integrations (such as with Modals) require receiving the JSON of an existing surface and then modifying or replacing that surface with another. You can "hydrate" the JSON of a surface (or element) into its object representation using its fromArray method (or fromJson).
$messageJson = <<<JSON
{
"blocks": [
{
"type": "section",
"block_id": "block1",
"text": {
"type": "mrkdwn",
"text": "*foo bar*"
}
}
}
}
JSON;
// Use fromArray to hydrate the message from parsed JSON data.
$decodedMessageJson = json_decode($messageJson, true);
$message = Message::fromArray($decodedMessageJson);
// OR... use fromJson to hydrate from a JSON string.
$message = Message::fromJson($messageJson);
Message Formatting
The Formatter class exists to provide helpers for formatting "mrkdwn" text. These helpers can be used so that you don't have to have the Slack mrkdwn syntax memorized. Also, these functions will properly escape <, >, and & characters automatically, if it's needed.
Example:
// Note: $event is meant to represent some kind of DTO from your own application.
$fmt = Kit::formatter();
$msg = Kit::newMessage()->text($fmt->sub(
'Hello, {audience}! On {date}, {host} will be hosting an AMA in the {channel} channel at {time}.',
[
'audience' => $fmt->atHere(),
'date' => $fmt->date($event->timestamp),
'host' => $fmt->user($event->hostId),
'channel' => $fmt->channel($event->channelId),
'time' => $fmt->time($event->timestamp),
]
));
Example Result:
{
"blocks": [
{
"type": "section",
"text": {
"type": "mrkdwn",
"text": "Hello, <!here>! On <!date^1608322949^{date}|2020-12-18T20:22:29+00:00>, <@U12345678> will be hosting an AMA in the <#C12345678> channel at <!date^1608322949^{time}|2020-12-18T20:22:29+00:00>."
}
}
]
}
Virtual Elements
In addition to the standard Block Kit 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
The Kit façade provides ways to create surfaces. Surfaces contain one or more blocks. Blocks are the primary element of the Block Kit. Blocks contain other elements, including other blocks, inputs (interactive elements), and partials (element parts that are not uniquely identifiable).
See the YUML
[Kit]-creates>[Surface]
[Surface]^[Message]
[Surface]^[Modal]
[Surface]^[AppHome]
[Surface]^[Attachment]
[Element]^[Surface]
[Element]^[Block]
[Element]^[Input]
[Element]^[Partial]
[Surface]<>->[Block]
[Message]<>->[Attachment]
[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, add tests, improve, etc.
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 $text): self).- Should return
selfto support chaining. - Should set the parent (e.g.,
setParent()) of the sub-element to$this.
- Should return
- 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
selfto support chaining. - Should have a maximum of 2 parameters.
- Should call the regular setter (e.g.,
return $this->setText(new PlainText($title));).
- Should be in addition to the
- To set other non-element properties, provide a simple setter method (e.g.,
url(string $url): self).- Should be named after the property being set.
- Should return
selfto support chaining.
- To create new sub-elements attached to the current one, provide a
new-prefixed factory method (e.g.,newImage(): Image).- Should return an instance of the sub-element.
- Should set the parent (e.g.,
setParent()) of the sub-element to$thisbefore returning. - Should support a
$blockIdparameter if it's a Block or an$actionIdparameter if it's an Input element.
- All element types should be defined in the
Typeclass 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.
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