php 关键词过滤

$badword = array(    
    '张三','张三丰','张三丰田'    
);    
$badword1 = array_combine( $badword, array_fill(0, count($badword), '*') );    
$bb = '我今天开着张三丰田上班';    
$str = strtr($bb, $badword1);    
echo $str;