twigphp/Twig · error · Twig\Error\RuntimeError

InlineStyle can only be created from iterable values.

Error message

InlineStyle can only be created from iterable values.

What it means

InlineDialeStyle/InlineStyle is a Twig html-extra value object representing CSS inline styles; its constructor only accepts iterable values (arrays, Traversables) which are spread into a list of style declarations. Passing a scalar or null raises this RuntimeError so malformed style data fails fast instead of producing broken HTML attributes.

Solutions

Pass an array or Traversable of style declarations, e.g. new InlineStyle(['color' => 'red']).
Explode a CSS string yourself into an array before constructing.
Guard the value for null/empty before constructing.

Example fix

// before
$style = new InlineStyle('color:red; font-weight:bold');
// after
$style = new InlineStyle(['color' => 'red', 'font-weight' => 'bold']);

Defensive patterns

Strategy: type-guard

Validate before calling

if (!is_iterable($value)) {
    throw new InvalidArgumentException('InlineStyle requires an iterable of style declarations');
}
$style = new InlineStyle($value);

Type guard

function isIterableForInlineStyle(mixed $v): bool {
    return is_iterable($v);
}

Try / catch

try {
    $style = new InlineStyle($value);
} catch (\Twig\Error\RuntimeError $e) {
    if (str_contains($e->getMessage(), 'InlineStyle can only be created')) {
        $style = new InlineStyle((array) ($value ?? []));
    } else {
        throw $e;
    }
}

Prevention

Always construct InlineStyle from arrays of declarations, never raw CSS strings
Coerce nullable variables with ?? [] before constructing
Document that the style() helper expects iterables

When it happens

Trigger: Calling new InlineStyle('color:red') (string), new InlineStyle(null), new InlineStyle(42), or passing a non-iterable expression to a style attribute in a template via the html-style style() helper.

Common situations: Passing a raw CSS string instead of an array of declarations, or a variable that is null because a lookup failed.

Understand the failure class

Background: Type mismatch errors: IllegalArgumentException, TypeError and type guards across 150 open-source libraries — this error's family across 150 libraries.

Related errors

AI-assisted analysis of twigphp/Twig@a414c3a491 (2026-09-13). Data as JSON: /api/errors/f237172a620be91f. Report an issue: GitHub.

Appendix: source

Thrown at extra/html-extra/HtmlAttr/InlineStyle.php:26

 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Twig\Extra\Html\HtmlAttr;

use Twig\Error\RuntimeError;

/**
 * @author Matthias Pigulla <mp@webfactory.de>
 */
final class InlineStyle implements MergeableInterface, AttributeValueInterface
{
    private readonly array $value;

    public function __construct(mixed $value)
    {
        if (!is_iterable($value)) {
            throw new RuntimeError('InlineStyle can only be created from iterable values.');
        }

        $this->value = [...$value];
    }

    public function mergeInto(mixed $previous): mixed
    {
        if ($previous instanceof self) {
            return new self([...$previous->value, ...$this->value]);
        }

        if (is_iterable($previous)) {
            return new self([...$previous, ...$this->value]);
        }

        throw new RuntimeError('Attributes using InlineStyle can only be merged with iterables or other InlineStyle instances.');
    }

View on GitHub (pinned to a414c3a491)