Contao\Environment::documentRoot PHP Method

    protected static function documentRoot()
    {
        $strDocumentRoot = '';
        $arrUriSegments = array();
        $scriptName = static::get('scriptName');
        $scriptFilename = static::get('scriptFilename');
        // Fallback to DOCUMENT_ROOT if SCRIPT_FILENAME and SCRIPT_NAME point to different files
        if (basename($scriptName) != basename($scriptFilename)) {
            return str_replace('//', '/', strtr(realpath($_SERVER['DOCUMENT_ROOT']), '\\', '/'));
        }
        if (substr($scriptFilename, 0, 1) == '/') {
            $strDocumentRoot = '/';
        }
        $arrSnSegments = explode('/', strrev($scriptName));
        $arrSfnSegments = explode('/', strrev($scriptFilename));
        foreach ($arrSfnSegments as $k => $v) {
            if (@$arrSnSegments[$k] != $v) {
                $arrUriSegments[] = $v;
            }
        }
        $strDocumentRoot .= strrev(implode('/', $arrUriSegments));
        if (strlen($strDocumentRoot) < 2) {
            $strDocumentRoot = substr($scriptFilename, 0, -(strlen($strDocumentRoot) + 1));
        }
        return str_replace('//', '/', strtr(realpath($strDocumentRoot), '\\', '/'));
    }