Troubleshooting

Last updated Oct 3, 20266 min read

First steps

Turn on WP_DEBUG and WP_DEBUG_LOG in wp-config.php. Every expression that fails is logged to wp-content/debug.log:

[wpmcf] Variable resolution failed — "{{ 1 + 2 }}" — Unexpected character: +

Failures are silent for visitors and editors; without debug the block is just empty.

Test the expression on its own, in a template or with WP-CLI:

bash

wp eval 'echo wpmcf_resolve_variables( "{{ glb.phone | default(\"missing\") }}" );'

List what the engine knows (names are lowercase):

php

$registry = wpmcf_variable_registry();
var_dump( $registry->getRegisteredNamespaces(), $registry->getRegisteredFilters(), $registry->getRegisteredFunctions() );

The expression prints nothing

Cause	Check	Fix
Syntax error	`WP_DEBUG` log shows the reason	See Syntax. Common: arithmetic (`1 + 2`), `!`, a missing quote or parenthesis, a `\|` with no filter name.
Negative number literal	`fn.abs(-5)`, `fn.substr('abc', -1)`	`-` is not a valid character. Pass the number from a field or a nested block.
Unknown key	`{{ glb.phon }}`	Check the key. Unknown names are empty by design; add `\| default('…')` to see the fallback.
An old key with a hyphen or a leading digit	`{{ glb.my-key }}`, `{{ glb.2fa }}`	New saves of such keys are refused (`422`), but older ones may remain. Rename the Global Data key to lowercase letters, digits and underscores starting with a letter. `wpmcf_get_global( 'my-key' )` still works.
The value is a password	A Password field or a password Global Data variable	Never available in a template. See Security.
No object	`{{ fg.group.field }}` or `{{ wp.post_title }}` outside a post	Pass a context: `wpmcf_resolve_variables( $t, wpmcf_make_context( $post_id ) )`.
`woo.*` on a non-product	WooCommerce inactive, or the object is not a product	Use it only on product contexts.
The block is too long or too deep	More than 1000 characters, 5 nested blocks or 32 levels	Split it into several blocks or move the logic into PHP.
A function was called through another namespace	`{{ wp.upper('a') }}`	Functions are called as `fn.upper('a')`.

The braces show up on the page

The text printed as stored: the value was not evaluated.

Cause	Fix
The post's author does not have `unfiltered_html` (author, contributor, any role without it, or any non-super-admin on multisite)	Have a trusted user save the value, or allow it with the `wpmcf/field/resolve_variables` filter.
The value is a comment field	Never evaluated. Use a post, term, user or options value.
The text is inside a Group, Repeater or Flexible content field	Only top-level text values are evaluated. Put the expression in the group's own template text or read the sub value with `{{ fg.group.field.sub }}`.
The text is post content or a title	Core content is not evaluated. Use `[wpmcf_field]`, `[wpmcf_global]` or the field block instead.
The text is read through REST, GraphQL, an export file or an admin list column	These show the stored text.
The braces come out of a variable	A value that itself contains `{{ }}` is inserted as is when read with `{{ glb.* }}` or `{{ fg.* }}`. Read the variable directly (`wpmcf_get_global()`) to evaluate its own expressions, one level.
An Elementor widget is shown in the editor	Widgets that Elementor previews with JavaScript templates (Heading, Button) show the raw text in the editor. The live page resolves it.
A block was never closed (`{{ glb.name`)	Add the closing `}}`.

The output is the wrong value

Symptom	Cause	Fix
A number is not formatted	The value is not numeric (`1,234`, `12 EUR`) and the number filters pass non-numbers through	Store plain numbers; format with `number()`
`{{ x \| length }}` is `0` for a number	`length` counts text and lists only	Store the value as text (a Text field, a Global Data text variable)
`{{ x \| date('Y') }}` shows 1970 or a strange year	A value like `20260517` is numeric, so it is read as a Unix timestamp	Store dates as `2026-05-17`
`{{ 0 \| default('n/a') }}` prints `0`	`default` only replaces nothing, `''` and `false`	Use `if_empty` to replace `0` too
`{{ a < b < c }}` or a chained ternary	Only the first comparison or ternary is read	Use `&&` or `fn.if()`
`wp.post_title` is empty in a term, user, comment or options value	`wp.post_*` resolves only in a post context	Read what you need with `fg` or `glb`, or use a post value
`wp.term_name` is empty	The value is not a term value, and no `term_id` meta is set	Use it in a term field value, or `wpmcf_make_context( $id, 'term' )`
`fn.rand()` or `fn.now()` changes on every load	They are evaluated each time	Do not use them on cached pages
A date is in English	Dates use the site language (Settings › General)	Change the site language
`{{ glb.tags }}` prints `red, green, blue`	Lists are printed joined by `,`	`\| join(' / ')` for another separator

The output contains HTML or breaks my markup

Variable results are not escaped. In a template, escape at the output:

php

echo esc_html( wpmcf_resolve_variables( '{{ glb.company }}' ) );

wpmcf_the_field() and [wpmcf_field] escape for you. In an expression use \| escape, \| esc_attr or \| strip_tags. See Security.

A page shows one person's name to everybody

The page must not be cached. The plugin already marks a front-end page that prints a wp.user_* variable as not cacheable (DONOTCACHEPAGE and no-cache headers). If your cache layer ignores both (a CDN or a server-level cache), exclude that URL from it, or remove wp.user_* from the page.

My custom namespace, filter or function does nothing

Cause	Fix
The `wpmcf/variables/register` listener was added too late. It fires once, when the registry is built after boot.	Attach it when your plugin file loads or on `plugins_loaded`. If you cannot, call `wpmcf_variable_registry()->registerFilter( … )` directly.
The resolver returns `null`	`null` prints nothing. Return a string or a number.
The name is taken or reserved	`fn`, `func`, `fonk`, `function` are reserved. Registering an existing name replaces it.
The name has a dash or a leading digit	Names are letters, digits and underscores, starting with a letter.

`fn.option()` returns nothing

The option is not on the allow-list. See Filters and functions. Add a safe public option with wpmcf/variables/allowed_options.

A hook does not fire

Cause	Fix
Wrong number of arguments	Pass the fourth argument of `add_action()` / `add_filter()`: `add_filter( 'wpmcf/field/value', $cb, 10, 5 )`.
Listener attached too late	Registration hooks (`variables/register`, `field_types/register`, `admin/register_pages`, `builders/components`) fire once when their registry is first used. Attach on `plugins_loaded` or earlier.
The hook is a Pro hook on a free build or an unlicensed site	Hooks marked Pro in the reference exist only with Pro code and a license or trial.
The hook name is a scheduled action	`wpmcf/tasks/run`, `wpmcf/tasks/watchdog`, `wpmcf/fields/schema_change`, `wpmcf/field_groups/code_sync` and `wpmcf/acf/migrate` are internal; do not listen to them. Use `wpmcf/tasks/finished` and friends.
`wpmcf/fields/copy_object` is never called	It is a hook you fire; the plugin only listens.
The filter returns nothing	A filter must return the value. A missing `return` passes `null` to the plugin.

To see every wpmcf/ hook firing during a request while you debug:

php

add_action( 'all', function ( $hook ) {
    if ( str_starts_with( $hook, 'wpmcf/' ) ) {
        error_log( 'hook: ' . $hook );
    }
} );

Still stuck

Open Settings › Health in the plugin: it lists errors the plugin caught, with the module and the file and line. See Health and troubleshooting.

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