php里怎么实现javascript的unescape函数的功能?

function escape($str) {
preg_match_all("/[\x80-\xff]. ¦[\x01-\x7f]+/",$str,$r);
$ar = $r[0];
foreach($ar as $k=>$v) {
if(ord($v[0]) < 128)
$ar[$k] = rawurlencode($v);
else
$ar[$k] = "%u".bin2hex(iconv("GB2312","UCS-2",$v));
}
return join("",$ar);
}

function unescape($str) {
$str = rawurldecode($str);
preg_match_all("/(?:%u.{4}) &brvbar.+/",$str,$r);
$ar = $r[0];
foreach($ar as $k=>$v) {
if(substr($v,0,2) == "%u" && strlen($v) == 6)
$ar[$k] = iconv("UCS-2","GB2312",pack("H4",substr($v,-4)));
}
return join("",$ar);
}

要求iconv函数可用（iconv扩展库已加载），否则需要自行编程查表