Blocks and Block Bindings

Last updated Oct 3, 20266 min read

Two ways to show field values in the block editor, both free:

	WPM Field block (`wpmcf/field`)	WPM Fields Block Bindings source (`wpmcf/field`)
What it is	A dynamic block of its own	A data source for attributes of core blocks
Best for	Print a field with prefix, suffix, fallback, link or image	Make a paragraph, heading, button or image be the field
Output	`<div class="wp-block-wpmcf-field">...</div>`	the core block's own markup
Works in query loops	yes	yes

Both read from the current post, or from each post in a Query Loop, and both use the same field catalog. Password fields never appear in either.

References: `group.field[.path]`

Both take a field reference of the form group_key.field_key, optionally followed by a path into a Group or Repeater value:

listing.price
listing.details.city       (Group field "details", sub-field "city")
listing.items.0.name       (Repeater "items", first row, sub-field "name")

References are lower-cased and cleaned with sanitize_key() per segment. A reference that does not name a visible field renders as empty. A group that appears only on options pages reads the options value and needs no post.

The WPM Field block

Insert WPM Field (category Text, keywords "custom field", "meta", "dynamic") and pick a field in the sidebar. The block is dynamic: it is rendered on the server each time.

Attributes

Attribute	Type	Default	Description
`field`	string	`""`	The field reference. Empty prints nothing (or the fallback).
`format`	`auto`, `text`, `link`, `image`	`auto`	See below. Any other value is treated as `auto`.
`prefix`	string	`""`	Text before the value, in `<span class="wpmcf-field-block__prefix">`. Escaped.
`suffix`	string	`""`	Text after the value, in `<span class="wpmcf-field-block__suffix">`. Escaped.
`imageSize`	string	`large`	Image size name for `format` image.
`linkText`	string	`""`	Label for `format` link. Empty uses the field's text, else the URL.
`fallback`	string	`""`	Printed (escaped) instead of the value when it is empty. Prefix and suffix are not added to a fallback.

Block supports: wide/full/left/center/right alignment, margin, padding, font size, line height, text and background color, link color.

In saved content:

html

<!-- wp:wpmcf/field {"field":"listing.price","prefix":"From ","suffix":" EUR","fallback":"Ask for a price"} /-->

Formats

`format`	Output
`auto`	The field type's own formatted, escaped HTML (a Select's label, a Link as `<a>`, an Image as `<img>`, a Repeater as a list).
`text`	The value as plain text, escaped. Markup the type adds is dropped.
`link`	`<a href="URL">label</a>`. The URL comes from URL, Link, Email (`mailto:`), File, Image, Page link, Post object and oEmbed fields. Label is `linkText`, else the field's text. Empty when the field has no URL.
`image`	The image of an Image field (or the first of a gallery) as `<img>` at `imageSize`. Empty for other fields, so the `fallback` shows.

Wrapper: the whole result is inside <div class="wp-block-wpmcf-field"> (plus the block's alignment, color and spacing classes). When there is nothing to print and no fallback, no markup at all is produced.

Verified outputs for a text value Hello <x> & "y" (stored as Hello & "y"):

html

<div class="wp-block-wpmcf-field">Hello &amp; &quot;y&quot;</div>
<div class="wp-block-wpmcf-field"><span class="wpmcf-field-block__prefix">&lt;P&gt; </span>Hello ...<span class="wpmcf-field-block__suffix"> S</span></div>

Which post

The block uses the Query Loop item (postId block context) when there is one, else the current post (get_the_ID()). Values are shown only when the viewer may see that post, with the same rule as WordPress's own post-meta binding: the post is publicly viewable or the viewer can read_post, and it is not password-protected. Otherwise the block prints nothing (or its fallback).

The "WPM Fields" Block Bindings source

Registered as source wpmcf/field with label WPM Fields (WordPress 6.5+). In the editor, select a core block, open the Attributes panel and bind an attribute to a field; the field list shows every field except Password and layout fields. In saved content a binding is block metadata:

html

<!-- wp:paragraph {"metadata":{"bindings":{"content":{"source":"wpmcf/field","args":{"key":"listing.title"}}}}} -->
<p>Placeholder</p>
<!-- /wp:paragraph -->

args.key is the field reference.

What each attribute receives

Attribute	Value
`url`, `href` (button and link attributes)	the field's URL (URL, Link, Email, File, Image, Page link, Post object, oEmbed fields; empty otherwise)
`core/image` `id`	the attachment ID of the Image field
`core/image` `url`	the image URL (falls back to the field's URL)
`core/image` `alt`	the attachment's alt text (falls back to the field's text)
anything else (`content`, `text`, `title`, ...)	the field's plain text

A url/href binding to a field that is not URL-like (plain text) gives an empty URL (verified).

Rich-text attributes (such as a paragraph's content) get the text HTML-escaped, so a literal < stays text (verified: a < b & c renders a < b & c). Attributes core outputs as attributes are escaped by core.

Verified examples:

Block and binding	Rendered
paragraph `content` to a text field	`<p class="wp-block-paragraph">Hello & "y"</p>`
heading `content`	`<h2 ...>Hello ...</h2>`
button `url` to a URL field, `text` to a text field	`<a href="https://example.com/p?x=1&y=2" class="wp-block-button__link ...">Hello ...</a>`
button `url` to a Link field	the Link field's URL
image `id`, `url`, `alt` to an Image field	the attachment's `<img>` with its alt text
paragraph bound to a Password or unknown field	an empty paragraph
paragraph bound to an options-only group	the options value (when the viewer may see it)

A missing field, an unknown reference or a hidden post gives an empty value: the placeholder text is not kept, so the block renders empty.

Which post

Same as the block: Query Loop item, else the current post, visible to the viewer, else empty.

Options-page values

A reference to a field of a group shown only on options pages works in both the block and bindings, with or without a post. Inside post content, the post author must have the options capability (manage_options by default, or what wpmcf/options/capabilities returns), the same rule as the shortcode. Outside post content during REST requests (editor previews), the current user needs it.

Editor REST routes (internal)

The editor script loads data from two wpmcf/v1 routes. They are for the block UI, not a public API.

Route	Method	Permission	Purpose
`/wpmcf/v1/blocks/fields?kind=text\|url\|image`	GET	`edit_posts`	The field catalog (`ref`, `label`, `group`, `type`) for a kind of use. `kind` defaults to `text`; other values are rejected (400).
`/wpmcf/v1/blocks/values`	POST	`edit_posts` and `read_post` on `postId`	Live values for the bindings preview: `{ "postId": 5, "keys": ["g.f", ...] }` (max 50 keys), returns `{ "values": { "g.f": { "text", "url", "image" } } }`.

Verified: admin and editor get 200, a subscriber 403, a logged-out request 401.

Troubleshooting

Symptom	Cause
The block shows nothing on the site but works in the editor	The field is empty, the post is private or password-protected for the viewer, or you are outside a post (no `postId`). Set a fallback to see it.
The field is missing from the picker	It is a Password or layout (tab, accordion) field, or the field group is inactive.
"WPM Fields" is missing in the Attributes panel	The block does not support bindings, or WordPress is older than 6.5 (the plugin requires 6.6).
An image field prints the file URL as text	Use `format` image on the block, or bind `id`/`url`/`alt` of a core Image block.

Page-builder equivalents (Elementor, Bricks, Divi, Breakdance, Oxygen) are in Integrations.

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Blocks and Block Bindings

References: group.field[.path]

The WPM Field block

Attributes

Formats

Which post

The "WPM Fields" Block Bindings source

What each attribute receives

Which post

Options-page values

Editor REST routes (internal)

Troubleshooting

References: `group.field[.path]`