private $_str = ''; // 源字符串
private $_allow = array(); // 允许保留的属性 例如:array('id','class','title')
private $_exception = array(); // 特例 例如:array('a'=>array('href','class'),'span'=>array('class'))
private $_ignore = array(); // 忽略过滤的标记 例如:array('span','img')

/** 处理HTML,过滤不保留的属性

• @param String $str 源字符串

• @return String
  */
  public function strip($str){
  $this->_str = $str;

  if(is_string($this->_str) && strlen($this->_str)>0){ // 判断字符串

  $this->_str = strtolower($this->_str); // 转成小写

  $res = $this->findElements();
  if(is_string($res)){
  return $res;
  }
  $nodes = $this->findAttributes($res);
  $this->removeAttributes($nodes);
  }
  return $this->_str;
  }

/** 设置允许的属性

• @param Array $param
  */
  public function setAllow($param=array()){
  $this->_allow = $param;
  }

/** 设置特例

• @param Array $param
  */
  public function setException($param=array()){
  $this->_exception = $param;
  }

/** 设置忽略的标记

• @param Array $param
  */
  public function setIgnore($param=array()){
  $this->_ignore = $param;
  }

/* 搜寻需要处理的元素 /
private function findElements(){
$nodes = array();
preg_match_all("/<([^ !\/>\n]+)([^>]*)>/i",$this->_str,$elements);
foreach($elements[1] as $el_key => $element){
if($elements[2][$el_key]){
$literal = $elements[0][$el_key];
$element_name = $elements[1][$el_key];
$attributes = $elements[2][$el_key];
if(is_array($this->_ignore) && !in_array($element_name,$this->_ignore)){
$nodes[] = array('literal'=>$literal,'name'=>$element_name,'attributes'=>$attributes);
}
}
}

if(!$nodes[0]){ 
  return $this->_str; 
}else{ 
  return $nodes; 
} 

}

/** 搜寻属性

• @param Array $nodes 需要处理的元素
  /
  private function findAttributes($nodes){
  foreach($nodes as &$node){
  preg_match_all("/([^ =]+)\s=\s[\"|']{0,1}([^\"'])[\"|']{0,1}/i",$node['attributes'],$attributes);
  if($attributes[1]){
  foreach($attributes[1] as $att_key=>$att){
  $literal = $attributes[0][$att_key];
  $attribute_name = $attributes[1][$att_key];
  $value = $attributes[2][$att_key];
  $atts[] = array('literal'=>$literal,'name'=>$attribute_name,'value'=>$value);
  }
  }else{
  $node['attributes'] = null;
  }
  $node['attributes'] = $atts;
  unset($atts);
  }
  return $nodes;
  }

/** 移除属性

• @param Array $nodes 需要处理的元素
  */
  private function removeAttributes($nodes){
  foreach($nodes as $node){
  $node_name = $node['name'];
  $new_attributes = '';
  if(is_array($node['attributes'])){
  foreach($node['attributes'] as $attribute){
  if((is_array($this->_allow) && in_array($attribute['name'],$this->_allow)) || $this->isException($node_name,$attribute['name'],$this->_exception)){
  $new_attributes = $this->createAttributes($new_attributes,$attribute['value']);
  }
  }
  }
  $replacement = ($new_attributes) ? "<$node_name $new_attributes>" : "<$node_name>";
  $this->_str = preg_replace('/'.$this->protect($node['literal']).'/',$replacement,$this->_str);
  }
  }

/** 判断是否特例

• @param String $element_name 元素名
• @param String $attribute_name 属性名
• @param Array $exceptions 允许的特例
• @return boolean
  */
  private function isException($element_name,$attribute_name,$exceptions){
  if(array_key_exists($element_name,$this->_exception)){
  if(in_array($attribute_name,$this->_exception[$element_name])){
  return true;
  }
  }
  return false;
  }

/** 创建属性

• @param String $new_attributes
• @param String $name
• @param String $value
• @return String
  */
  private function createAttributes($new_attributes,$name,$value){
  if($new_attributes){
  $new_attributes .= " ";
  }
  $new_attributes .= "$name=\"$value\"";
  return $new_attributes;
  }

/** 特殊字符转义

• @param String $str 源字符串
• @return String
  /
  private function protect($str){
  $conversions = array(
  "^" => "\^","[" => "[","." => ".","$" => "\$","{" => "{","" => "*","(" => "(","\" => "\\","/" => "\/","+" => "+",")" => ")","|" => "|","?" => "\?","<" => "\<",">" => ">"
  );
  return strtr($str,$conversions);
  }

} // class end

?>

$str = '<div class="bd clearfix" id="index_hilite_ul"><ul class="list">