phalcon/cphalcon · error · Phalcon\Tag\Exception

Only scalar values can be assigned to UI components

Error message

Only scalar values can be assigned to UI components

What it means

Phalcon\Tag::setDefault() seeds default values that tag helpers use to pre-fill form fields. Because every default is later echoed into HTML markup, only scalars are usable; an array or object value throws Phalcon\Tag\Exception ('Only scalar values can be assigned to UI components'). null is explicitly allowed and is the supported way to clear a default.

Source

Thrown at phalcon/Tag.zep:1122

        return Select::selectField(parameters, data);
    }

    /**
     * Set autoescape mode in generated HTML
     */
    public static function setAutoescape(bool autoescape) -> void
    {
        let self::autoEscape = autoescape;
    }

    /**
     * Assigns default values to generated tags by helpers
     */
    public static function setDefault( string id, value) -> void
    {
        if value !== null {
            if unlikely (typeof value == "array" || typeof value == "object") {
                throw new Exception(
                    "Only scalar values can be assigned to UI components"
                );
            }
        }

        let self::displayValues[id] = value;
    }

    /**
     * Assigns default values to generated tags by helpers
     *
     * @phpstan-param tag_display_values $values
     */
    public static function setDefaults( array values, bool merge = false) -> void
    {
        if merge && typeof self::displayValues == "array" {
            let self::displayValues = array_merge(self::displayValues, values);
        } else {

View on GitHub (pinned to b7419de9cd)

Solutions

1. Assign the scalar field: Tag::setDefault('name', $user->name)
2. For objects that must appear, format them to string first — cast or call a __toString()-bearing method
3. If the value is a list, it belongs in the helper's options (e.g. select options), not in setDefault

Example fix

// before
\Phalcon\Tag::setDefault('category', $categories); // array -> throws

// after
\Phalcon\Tag::setDefault('category', (int) $request->get('category', 'int', 0));

if (is_object($value) && method_exists($value, '__toString')) {
    $value = (string) $value;
}

if (null === $value || is_scalar($value)) {
    \Phalcon\Tag::setDefault('name', $value);
}

function isScalarTagDefault($value): bool
{
    return null === $value || is_scalar($value);
}

When it happens

Trigger: Tag::setDefault('category', ['fruits', 'vegetables']); Tag::setDefault('user', $user) — assigning an object/Resultset instead of a field; arrays leaking in from request->getPost() when a field was submitted multiple times.

Common situations: Pre-filling a select's default with its options array instead of the selected key; assigning model objects rather than model properties; defaults sourced from decoded JSON whose values are nested arrays.

Related errors

• The 'using' parameter is required
• Form '{name}' is not registered in the FormsLocator
• Unknown form element type "{type}"
• Form schema definition at index {index} must be an array
• Form schema definition at index {index} is missing required

AI-assisted analysis of phalcon/cphalcon@b7419de9cd (2026-08-21). Data as JSON: /api/errors/c7fb27c659789ead. Report an issue: GitHub.