JetEngine Listings callback

Add a Dynamic Field transform through JetEngine's allowlist. Treat the callback as render code: make it deterministic, cheap, and explicit about whether it returns plain text or already-safe HTML.

When to use this skill

• Add a formatter to Dynamic Field's Filter field output control.
• Add callback-specific controls and positional PHP arguments.
• Diagnose a selected callback that yields blank or malformed output.
• Process serialized arrays, chained callbacks, HTML, or zero-valued settings.
• Audit output escaping or N+1 work in Listing Grids.

Preferred registration

Register on jet-engine/callbacks/register. The identifier must pass is_callable() and JetEngine's allowed-callback gate. Use a global function or a fully qualified static callable string.

final class My_Plugin_JE_Callbacks {
    public static function format_distance($value, $decimals = 1, $unit = 'km') {
        if (! is_numeric($value)) {
            return '';
        }

        $decimals = max(0, min(6, (int) $decimals));
        $unit     = in_array($unit, array('km', 'mi'), true) ? $unit : 'km';

        return number_format_i18n((float) $value, $decimals) . ' ' . $unit;
    }
}

add_action(
    'jet-engine/callbacks/register',
    static function($manager): void {
        $manager->register_callback(
            'My_Plugin_JE_Callbacks::format_distance',
            __('Format distance', 'my-plugin'),
            array(
                'my_plugin_decimals' => array(
                    'label'   => __('Decimals', 'my-plugin'),
                    'type'    => 'number',
                    'default' => 1,
                ),
                'my_plugin_unit' => array(
                    'label'   => __('Unit', 'my-plugin'),
                    'type'    => 'select',
                    'default' => 'km',
                    'options' => array(
                        'km' => 'km',
                        'mi' => 'mi',
                    ),
                ),
            )
        );
    }
);

JetEngine calls the function as:

callback(field value, my_plugin_decimals, my_plugin_unit)

Control declaration order is argument order. Prefix every control key. The modern registration adds its own UI conditions; do not duplicate them.

Critical argument edge

In 3.8.14, modern argument extraction uses ! empty($settings[$key]). Saved 0, '0', false, and '' therefore fall back to the declared default. The default is read with ! empty() too, so a declared default of 0 becomes an empty string. If zero is valid:

• choose a non-ambiguous UI representation and normalize it in the callback; or
• use the legacy jet-engine/listing/dynamic-field/callback-args filter and array_key_exists() for that argument.

Do not promise that a numeric control can pass literal zero through the modern helper unchanged.

Input and output contract

• The first argument is the current field result.
• Multiple filter_callbacks run sequentially; each output becomes the next callback's input.
• Return string, number, null, or WP_Error intentionally. Raw arrays and objects produce a visible JetEngine error with available child keys; they are not silently stringified.
• Return an empty string for unsupported input only when hiding the value is the desired behavior. Otherwise return a WP_Error during development.
• Bound database/remote work. A Listing Grid may invoke the callback once per field, per item, and per callback in the chain.

Serialized and array-backed values

JetEngine only safely unserializes input for callbacks listed by jet-engine/listings/non-scalar-callbacks. Add a custom callback only when its source field is documented to store arrays:

add_filter(
    'jet-engine/listings/non-scalar-callbacks',
    static function(array $callbacks): array {
        $callbacks['My_Plugin_JE_Callbacks::join_labels'] = true;
        return $callbacks;
    }
);

Do not call unrestricted unserialize() in a callback. Validate the resulting shape and convert it to a scalar before returning.

Output security

Custom callback output is not automatically escaped by default. The filter jet-engine/listings/dynamic-field/kses-output defaults to false at the final render point.

• For plain text, return esc_html($text) if the callback owns final HTML rendering, or return a raw scalar only when the consuming format escapes it.
• For URLs/attributes, escape at the final attribute context; do not use esc_html() as a universal sanitizer.
• For intentional limited HTML, return wp_kses_post($html) or enable final KSES for the exact field settings.
• Never pass user-controlled shortcode or arbitrary callable names through.

add_filter(
    'jet-engine/listings/dynamic-field/kses-output',
    static function($use_kses, $settings) {
        return 'My_Plugin_JE_Callbacks::safe_badge'
            === ($settings['filter_callback'] ?? '') ? true : $use_kses;
    },
    10,
    2
);

Legacy route

Use the three legacy filters only for compatibility or zero-sensitive argument handling:

• jet-engine/listings/allowed-callbacks
• jet-engine/listings/allowed-callbacks-args
• jet-engine/listing/dynamic-field/callback-args

Keep the same fully callable identifier in all three. Read callback-contracts.md before implementing the legacy path or chained/non-scalar behavior.

Verification

Test direct is_callable(), allowlist presence, argument order, omitted values, literal zero, empty input, malicious HTML, array/object output, a multi-callback chain, and a multi-item Listing Grid. Confirm the actual rendered DOM and count queries, not only the callback's direct return value.

References

• Official documentation: https://crocoblock.com/knowledge-base/plugins/jetengine/
• Crocoblock developer documentation: https://github.com/Crocoblock/developer-documentation/tree/main/01-jet-engine
• Verified source paths:
  • wp-content/plugins/jet-engine/includes/components/listings/callbacks.php
  • wp-content/plugins/jet-engine/includes/components/listings/manager.php
  • wp-content/plugins/jet-engine/includes/components/listings/render/dynamic-field.php
  • wp-content/plugins/jet-engine/includes/core/functions.php