class 'domdocument' not found laravel when sending email

I am trying to send verification mail to user using mail system

Mail::to($thisUser->email)->send(new varifyEmail($thisUser));

but it gives me

Class 'DOMDocument' not found

this is the function that gives this error

protected function createDomDocumentFromHtml($html)
{
    $document = new \DOMDocument('1.0', 'UTF-8'); // this is the line with error
    $internalErrors = libxml_use_internal_errors(true);
    $document->loadHTML(mb_convert_encoding($html, 'HTML-ENTITIES', 'UTF-8'));
    libxml_use_internal_errors($internalErrors);
    $document->formatOutput = true;

    return $document;
}

can anyone help for this??