PHP字符过滤方法

function str_filter_replace($str)
{
    if (empty($str)) return false;
    $str = htmlspecialchars($str);
    $str = str_replace( ‘/‘, "", $str);
    $str = str_replace("\\", "", $str);
    $str = str_replace(">", "", $str);
    $str = str_replace("<", "", $str);
    $str = str_replace("<SCRIPT>", "", $str);
    $str = str_replace("</SCRIPT>", "", $str);
    $str = str_replace("<script>", "", $str);
    $str = str_replace("</script>", "", $str);
    $str=str_replace("select","select",$str);
    $str=str_replace("join","join",$str);
    $str=str_replace("union","union",$str);
    $str=str_replace("where","where",$str);
    $str=str_replace("insert","insert",$str);
    $str=str_replace("delete","delete",$str);
    $str=str_replace("update","update",$str);
    $str=str_replace("like","like",$str);
    $str=str_replace("drop","drop",$str);
    $str=str_replace("create","create",$str);
    $str=str_replace("modify","modify",$str);
    $str=str_replace("rename","rename",$str);
    $str=str_replace("alter","alter",$str);
    $str=str_replace("cas","cast",$str);
    $str=str_replace("&","&",$str);
    $str=str_replace(">",">",$str);
    $str=str_replace("<","<",$str);
    $str=str_replace(" ",chr(32),$str);
    $str=str_replace(" ",chr(9),$str);
    $str=str_replace("    ",chr(9),$str);
    $str=str_replace("&",chr(34),$str);
    $str=str_replace("‘",chr(39),$str);
    $str=str_replace("<br />",chr(13),$str);
    $str=str_replace("‘‘","‘",$str);
    $str=str_replace("css","‘",$str);
    $str=str_replace("CSS","‘",$str);
    return $str;
}