AssetManager\Asset\AggregateAsset::processContent PHP Method

    private function processContent($content)
    {
        $this->mimetype = null;
        foreach ($content as $asset) {
            if (null === $this->mimetype) {
                $this->mimetype = $asset->mimetype;
            }
            if ($asset->mimetype !== $this->mimetype) {
                throw new Exception\RuntimeException(sprintf('Asset "%s" doesn\'t have the expected mime-type "%s".', $asset->getTargetPath(), $this->mimetype));
            }
            $this->setLastModified(max($asset->getLastModified(), $this->getLastModified()));
            $this->setContent($this->getContent() . $asset->dump());
        }
    }