Google\Cloud\Dev\DocGenerator\Command\Docs::getFilesList PHP Method

    private function getFilesList($source)
    {
        $directoryIterator = new RecursiveDirectoryIterator($source);
        $iterator = new RecursiveIteratorIterator($directoryIterator);
        $regexIterator = new RegexIterator($iterator, '/^.+\\.php|^.+\\.md$/i', RecursiveRegexIterator::GET_MATCH);
        $files = [];
        foreach ($regexIterator as $item) {
            array_push($files, $item[0]);
        }
        return $files;
    }