function stringBetween($string, $keyword)
{
    $matches = array();
    $keyword = preg_quote($keyword, '~');

    if (preg_match_all('~' . $keyword . '(.*?)' . $keyword . '~s', $string, $matches) > 0) {
        return $matches[1];
    } else {
        return 'No matches found!';
    }
}

$smsbody = '***name***';
$pl = stringBetween($smsbody, '***');
if (count($pl) > 0) {
    foreach ($pl as $str) {
        $new = '{$' . $str . '}';
        $smsbody = str_ireplace('***' . $str . '***', $new, $smsbody);
    }
}