php下過濾HTML代碼的函數

/*----------------------
過濾HTML代碼的函數
-----------------------*/
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);
    $string=str_replace("&lt;","<",$string);
    $string=str_replace("<","<",$string);
    $string=str_replace("&gt;",">",$string);
    $string=str_replace(">",">",$string);
    $string=str_replace("&nbsp;"," ",$string);
    $string=nl2br($string);
    return $string;
}