Zend Framework实现自定义过滤器的方法

<?php
require_once 'zend/filter/interface.php';
class myfilter implements zend_filter_interface{
 public function filter($value){
  $badlist = array("梨","草莓","苹果");
  for($i = 0;$i<count($badlist);$i++){
   $value = str_replace($badlist[$i], "*", $value);
  }
  return $value;
 }
}
$filter = new myfilter();
$temp1 = "桔子真好吃";
$temp2 = "我喜欢吃苹果";
$temp3 = "梨也不错，但我最喜欢吃的是草莓！";
echo "内容：".$temp1."<p>经过过滤后为：";
echo $filter->filter($temp1);
echo "<p>";
echo "内容：".$temp2."<p>经过过滤后为：";
echo $filter->filter($temp2);
echo "<p>";
echo "内容：".$temp3."<p>经过过滤后为：";
echo $filter->filter($temp3);
echo "<p>";