yiisoft/yii2 · error · InvalidArgumentException

Argument $haystack must be an array or implement Traversable

Error message

Argument $haystack must be an array or implement Traversable

What it means

Error "Argument $haystack must be an array or implement Traversable" thrown in yiisoft/yii2.

Source

Thrown at framework/helpers/BaseArrayHelper.php:863

    /**
     * Check whether an array or [[Traversable]] contains an element.
     *
     * This method does the same as the PHP function [in_array()](https://www.php.net/manual/en/function.in-array.php)
     * but additionally works for objects that implement the [[Traversable]] interface.
     *
     * @param mixed $needle The value to look for.
     * @param iterable $haystack The set of values to search.
     * @param bool $strict Whether to enable strict (`===`) comparison.
     * @return bool `true` if `$needle` was found in `$haystack`, `false` otherwise.
     * @throws InvalidArgumentException if `$haystack` is neither traversable nor an array.
     * @see https://www.php.net/manual/en/function.in-array.php
     * @since 2.0.7
     */
    public static function isIn($needle, $haystack, $strict = false)
    {
        if (!static::isTraversable($haystack)) {
            throw new InvalidArgumentException('Argument $haystack must be an array or implement Traversable');
        }

        if (is_array($haystack)) {
            return in_array($needle, $haystack, $strict);
        }

        foreach ($haystack as $value) {
            if ($strict ? $needle === $value : $needle == $value) {
                return true;
            }
        }

        return false;
    }

    /**
     * Checks whether a variable is an array or [[Traversable]].
     *

View on GitHub (pinned to 66f00d18a2)

When it happens

Trigger: Thrown at framework/helpers/BaseArrayHelper.php:863 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of yiisoft/yii2@66f00d18a2 (2026-08-17). Data as JSON: /api/errors/cd248865ca0db375. Report an issue: GitHub.