用于解密形如
[code]%68%74%74%70%3a%2f%2f%64%62%2e%67%61%6d%65%72%73%6b%79%2e%63%6f%6d%2f%53%6f%66%74%2f%53%68%6f%77%53%6f%66%74%44%6f%77%6e%2e%61%73%70%3f%55%72%6c%49%44%3d%31%26%53%6f%66%74%49%44%3d%31%37%31%36%31[/code]
加密后的字符串

GB2312编码：
[code]
<?php
function unescape($str) {
$str = rawurldecode($str);
preg_match_all("/%u.{4}|&#x.{4};|&#d+;|.+/U",$str,$r);
$ar = $r[0];
foreach($ar as $k=>$v) {
if(substr($v,0,2) == "%u")
$ar[$k] = iconv("UCS-2","GBK",pack("H4",substr($v,-4)));
elseif(substr($v,0,3) == "&#x")
$ar[$k] = iconv("UCS-2","GBK",pack("H4",substr($v,3,-1)));
elseif(substr($v,0,2) == "&#") {
$ar[$k] = iconv("UCS-2","GBK",pack("n",substr($v,2,-1)));
}
}
return join("",$ar);
}
?>

UTF8编码：
<?php
function unescape($str){
$ret = '';
$len = strlen($str);
for ($i = 0; $i < $len; $i++){
if ($str[$i] == '%' && $str[$i+1] == 'u'){
$val = hexdec(substr($str, $i+2, 4));
if ($val < 0x7f) $ret .= chr($val);
else if($val < 0x800) $ret .= chr(0xc0|($val>>6)).chr(0x80|($val&0x3f));
else $ret .= chr(0xe0|($val>>12)).chr(0x80|(($val>>6)&0x3f)).chr(0x80|($val&0x3f));
$i += 5;
}
else if ($str[$i] == '%'){
$ret .= urldecode(substr($str, $i, 3));
$i += 2;
}
else $ret .= $str[$i];
}
return $ret;
}
?>
[/code]

调用方法
[code]$download= unescape($download);[/code]