RegExp to EXCLUDE strip HTML (FOR SOMME) comments

Try slapping a negative lookahead before the comment match, eg

function remove_html_comments($content="") {
    return preg_replace('/(?!<!--\s*\/?mfunc\s*' . W3TC_DYNAMIC_SECURITY . ')<!--(.|\s)*?-->/', '', $content);
}

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)