How to make container class in PHP

You can do this using below code.

 if ($slide_title) {
    $strret .= '<div class="container">';
                $strret .= '<a class="'.$slide_linkurl.'"><h2>'.$slide_title.'</h2></a>';
                $strret .= '<p>'.$str.'</p>'; 
                $strret .= '<a href="'.$slide_linkurl.'" class="da-link">'.$slide_linktext.'</a>'; 
    $strret .= '</div>';

    }