php下过滤HTML代码的函数

/*---------------------- 
过滤HTML代码的函数 
-----------------------*/ 
function htmlEncode($string) { 
  $string=trim($string); 
  $string=str_replace("&","&",$string); 
  $string=str_replace("'","'",$string); 
  $string=str_replace("&","&",$string); 
  $string=str_replace(""",""",$string); 
  $string=str_replace("\"",""",$string); 
  $string=str_replace("<","<",$string); 
  $string=str_replace("<","&lt;",$string); 
  $string=str_replace("&amp;gt;","&gt;",$string); 
  $string=str_replace(">","&gt;",$string); 
  $string=str_replace("&amp;nbsp;","&nbsp;",$string); 
  $string=nl2br($string); 
  return $string; 
}