PHP class to replace sensitive strings (source code attached)

/**string filter class
* Date: 2013-01-09
* Author: fdipzone
* Ver: v1.0
* Edit: bbs.it-home.org
* Func:
* public replace Replace illegal characters
* public check Check whether it contains illegal characters
* private protect_white_list protect the whitelist
* private resume_white_list restore the whitelist
* private getval whitelist key to value
*/
class StrFilter{ // class start

    private $_white_list = array();
    private $_black_list = array();
    private $_replacement = '*';
    private $_LTAG = '[[##';
    private $_RTAG = '##]]';

    /**
    * @param Array  $white_list
    * @param Array  $black_list
    * @param String $replacement
*/
    public function __construct($white_list=array(), $black_list=array(), $replacement='*'){
        $this->_white_list = $white_list;
        $this->_black_list = $black_list;
        $this->_replacement = $replacement;
    }

    /**Replace illegal characters
 * @param String $content The string to be replaced
 * @return String The replaced string
*/
    public function replace($content){

        if(!isset($content) || $content==''){
            return '';
        }

        // protect white list
        $content = $this->protect_white_list($content);

        // replace black list
        if($this->_black_list){
            foreach($this->_black_list as $val){
                $content = str_replace($val, $this->_replacement, $content);
            }
        }

        // resume white list
        $content = $this->resume_white_list($content);

        return $content;
    }

    /**Check whether it contains illegal self-characters
 * @param String $content string
 * @return boolean
*/
    public function check($content){

        if(!isset($content) || $content==''){
            return true;
        }

        // protect white list
        $content = $this->protect_white_list($content);

        // check
        if($this->_black_list){
            foreach($this->_black_list as $val){
                if(strstr($content, $val)!=''){
                    return false;
                }
            }
        }
        return true;
    }

    /**Protection whitelist
 * @param String $content string
 * @return String
*/
    private function protect_white_list($content){
        if($this->_white_list){
            foreach($this->_white_list as $key=>$val){
                $content = str_replace($val, $this->_LTAG.$key.$this->_RTAG, $content);
            }
        }
        return $content;
    }

    /**Restore whitelist
 * @param String $content
 * @return String
*/
    private function resume_white_list($content){
        if($this->_white_list){
            $content = preg_replace_callback("/[[##(.*?)##]].*?/si", array($this, 'getval'), $content);
        }
        return $content;
    }
    /**Whitelist key is restored to value
 * @param Array $matches matches the key of white_list
 * @return String white_list val
*/
    private function getval($matches){
        return isset($this->_white_list[$matches[1]])? $this->_white_list[$matches[1]] : ''; // key->val
    }

} // class end

?>

2，演示示例 demo.php

    header("content-type:text/html;charset=utf8");

    require("StrFilter.class.php");

    $white = array('屌丝', '曹操');
    $black = array('屌', '操');

    $content = "我操,曹操你是屌丝,我屌你啊";

    $obj = new StrFilter($white, $black);
    echo $obj->replace($content);
?>

附，php 替换敏感字符串的类源码下载地址。