php HTML str_replace SITE_TITLE isset site_title site_title Сантехника

<?php
$HTML   = str_replace( '#SITE_TITLE#' ,         (isset($site_title)         ?$site_title        :'Сантехника премиум класса | Трилит')  , ob_get_clean() );
$HTML   = str_replace( '#SITE_KEYWORDS#' ,      (isset($site_keywords)      ?$site_keywords     :'')                                    , $HTML );
$HTML   = str_replace( '#SITE_DESCRIPTION#' ,   (isset($site_description)   ?$site_description  :'')                                    , $HTML );
echo $HTML;
?>