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VOOZH | about |
This document describes the legacy attachment-based format for Slack messages, implemented through the SlackAttachment and SlackAttachmentField classes. This format predates Slack's modern Block Kit framework and is maintained for backwards compatibility with existing integrations.
For modern Slack message construction using Block Kit components, see Slack Block Kit. For an overview of Slack messaging capabilities, see Slack Messages.
Important: Slack has deprecated the attachment format in favor of Block Kit. New integrations should use Block Kit (documented in 6.5) instead. This legacy format is provided for maintaining existing implementations.
The legacy attachment system consists of three core classes that work together to create rich message content:
Diagram: Attachment Class Hierarchy
The SlackMessage class maintains an array of SlackAttachment objects, each of which can contain multiple SlackAttachmentField objects. Attachments are added using a closure-based fluent interface.
Sources: src/Messages/SlackMessage.php1-219 src/Messages/SlackAttachment.php1-284 src/Messages/SlackAttachmentField.php1-66
The SlackAttachment class provides a comprehensive set of properties for structuring rich message content:
| Property | Type | Description | Method |
|---|---|---|---|
title | ?string | Primary heading text | title(string, ?string) |
url | ?string | URL for title link | Set via title() |
pretext | ?string | Text above the attachment | pretext(string) |
content | ?string | Main text content | content(string) |
fallback | ?string | Plain-text summary | fallback(string) |
color | ?string | Left border color | color(string) |
fields | array | Array of field objects | field(), fields(array) |
markdown | array | Fields with markdown | markdown(array) |
imageUrl | ?string | Full-size image | image(string) |
thumbUrl | ?string | Thumbnail image | thumb(string) |
actions | array | Button actions | action(string, string, string) |
authorName | ?string | Author display name | author(string, ?string, ?string) |
authorLink | ?string | Author profile URL | Set via author() |
authorIcon | ?string | Author avatar URL | Set via author() |
footer | ?string | Footer text | footer(string) |
footerIcon | ?string | Footer icon URL | footerIcon(string) |
timestamp | int | Unix timestamp | timestamp(DateInterval|DateTimeInterface|int) |
callbackId | string | Interactive callback ID | callbackId(string) |
Sources: src/Messages/SlackAttachment.php16-105
Attachments are added to SlackMessage instances using the attachment() method, which accepts a closure that receives a SlackAttachment instance:
Diagram: Attachment Creation Flow
The SlackMessage::attachment() method creates a new SlackAttachment object, passes it to the provided closure for configuration, and appends it to the internal attachments array.
Sources: src/Messages/SlackMessage.php153-160 src/Messages/SlackAttachment.php160-175
The attachment title serves as the primary heading and can optionally include a hyperlink:
Diagram: Title Configuration
The title() method sets both the title text and an optional URL in a single call. The pretext() method adds text that appears above the attachment, while content() sets the main body text.
Sources: src/Messages/SlackAttachment.php109-115 src/Messages/SlackAttachment.php120-125 src/Messages/SlackAttachment.php130-135
The fallback property provides a plain-text alternative for clients that don't support rich attachments:
| Method | Purpose |
|---|---|
fallback(string) | Sets plain-text summary displayed in notifications and unfurls |
Sources: src/Messages/SlackAttachment.php140-145
The color() method sets the vertical border color on the left side of the attachment. This accepts hex color codes, named colors, or the special values good, warning, and danger:
Diagram: Color Options
Sources: src/Messages/SlackAttachment.php150-155
Fields organize information into structured key-value pairs that can be displayed side-by-side or stacked:
The SlackAttachmentField class has three properties:
| Property | Type | Default | Description |
|---|---|---|---|
title | ?string | null | Field label |
content | ?string | null | Field value |
short | bool | true | Display side-by-side if true |
Sources: src/Messages/SlackAttachmentField.php12-22
Fields can be added to attachments using two approaches:
Diagram: Field Addition Methods
The closure approach provides full control over field properties including the short flag, while the simple approach creates a basic key-value mapping.
Sources: src/Messages/SlackAttachment.php160-175
The long() method on SlackAttachmentField forces the field to display at full width rather than side-by-side:
Diagram: Field Width Control
Sources: src/Messages/SlackAttachmentField.php47-52
The markdown() method specifies which fields should be parsed for Markdown formatting:
Diagram: Markdown Configuration
Common field names for markdown parsing: pretext, text, fields.
Sources: src/Messages/SlackAttachment.php190-195
Attachments support two types of images:
| Method | Property | Display |
|---|---|---|
image(string) | imageUrl | Full-size image displayed within attachment |
thumb(string) | thumbUrl | Small thumbnail on the right side |
Sources: src/Messages/SlackAttachment.php200-205 src/Messages/SlackAttachment.php210-215
The action() method adds interactive buttons below the attachment:
Diagram: Action Button Structure
Each action creates a button with the specified text and URL. The style parameter controls the button's visual appearance.
Sources: src/Messages/SlackAttachment.php220-230
The author() method sets the author metadata displayed at the top of the attachment:
Diagram: Author Properties
All three properties are set in a single method call. The link makes the author name clickable, and the icon displays a small avatar.
Sources: src/Messages/SlackAttachment.php235-242
Footer components appear at the bottom of the attachment:
| Method | Property | Purpose |
|---|---|---|
footer(string) | footer | Footer text content |
footerIcon(string) | footerIcon | Small icon URL displayed next to footer |
Sources: src/Messages/SlackAttachment.php247-252 src/Messages/SlackAttachment.php257-262
The timestamp() method accepts multiple time formats using the InteractsWithTime trait:
Diagram: Timestamp Conversion
The availableAt() method from the InteractsWithTime trait normalizes all input formats to a Unix timestamp.
Sources: src/Messages/SlackAttachment.php267-272 src/Messages/SlackAttachment.php14
The callbackId() method sets an identifier for interactive message callbacks:
| Property | Default | Purpose |
|---|---|---|
callbackId | '' | Identifies the attachment in interactive responses |
Sources: src/Messages/SlackAttachment.php104 src/Messages/SlackAttachment.php277-282
The following diagram illustrates a complete attachment construction pattern:
Diagram: Complete Attachment Construction Sequence
This sequence demonstrates the typical pattern for constructing a rich attachment with title, colored border, multiple fields (including one long field), markdown support, metadata, and an action button.
Sources: src/Messages/SlackMessage.php153-160 src/Messages/SlackAttachment.php109-282 src/Messages/SlackAttachmentField.php27-52
The SlackAttachmentField::toArray() method converts the field object into the array format expected by Slack's API:
Diagram: Field Serialization
Note that the content property is serialized as value in the output array to match Slack's API expectations.
Sources: src/Messages/SlackAttachmentField.php57-64
The SlackMessage class stores attachments and provides the entry point for adding them:
Diagram: SlackMessage Attachment Storage
The attachments property is a simple array that accumulates all added attachments. Each call to attachment() creates a new SlackAttachment instance, configures it via the closure, and appends it.
Sources: src/Messages/SlackMessage.php59 src/Messages/SlackMessage.php153-160
Applications using legacy attachments should plan migration to Block Kit for several reasons:
| Consideration | Legacy Attachments | Block Kit |
|---|---|---|
| Status | Deprecated by Slack | Current standard |
| Interactivity | Limited (buttons only) | Full interactive components |
| Layout Control | Fixed structure | Flexible composition |
| Maintenance | Compatibility mode | Active development |
| Documentation | Slack API reference only | Block Kit documentation available |
The Block Kit system is documented in page 6.5, including block types (6.5.2) and interactive elements (6.5.3).
Sources: src/Messages/SlackAttachment.php1-284 (legacy implementation), 6.5 (modern replacement)
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