src/Zipkin/Propagation/Map.php
public function put(&$carrier, string $key, string $value): void
    {
        if ($key === '') {
            throw InvalidPropagationKey::forEmptyKey();
        }

        $lKey = strtolower($key);

        if ($carrier instanceof ArrayAccess || is_array($carrier)) {
            $carrier[$lKey] = $value;
            return;
        }

        throw InvalidPropagationCarrier::forCarrier($carrier);
    }
public function put(&$carrier, string $key, string $value): void
    {
        if ($key === '') {
            throw InvalidPropagationKey::forEmptyKey();
        }

        $lKey = strtolower($key);

        if ($carrier instanceof ArrayAccess || is_array($carrier)) {
            $carrier[$lKey] = $value;
            return;
        }

        throw InvalidPropagationCarrier::forCarrier($carrier);
    }
{@inheritdoc}
@param array|ArrayAccess $carrier