php中unicode字符怎么才能转换UTF-8？

貌似这个问题不是前几天才有人问过了吗
手册的iconv部分不是有的吗function unescape($str) {
    $str = rawurldecode($str);
    preg_match_all("/(?:%u.{4})|&#x.{4};|&#\d+;|.+/U",$str,$r);
    $ar = $r[0];
    //print_r($ar);
    foreach($ar as $k=>$v) {
        if(substr($v,0,2) == "%u")
            $ar[$k] = iconv("UCS-2","UTF-8",pack("H4",substr($v,-4)));
        elseif(substr($v,0,3) == "&#x")
            $ar[$k] = iconv("UCS-2","UTF-8",pack("H4",substr($v,3,-1)));
        elseif(substr($v,0,2) == "&#") {
            //echo substr($v,2,-1)."\n";
            $ar[$k] = iconv("UCS-2","UTF-8",pack("n",substr($v,2,-1)));
        }
    }
    return join("",$ar);
}die( unescape('%u9996%u9875') );