PHP加密/解密函数dencrypt(动态密文，带压缩功能，支持中文)

//+----------------------------------------------------------------------+
//|WillkoFramework|
//+----------------------------------------------------------------------+
//|Copyright(c)2008-2009WillkoCheng|
//+----------------------------------------------------------------------+
//|Authors:WillkoCheng<willko@foxmail.com>|
//+----------------------------------------------------------------------+
//$string明文或密文
//$isEncrypt是否加密
//$key密匙
//采用SHA1生成密匙簿，超过300个字符使用ZLIB压缩
functiondencrypt($string,$isEncrypt=true,$key=KEY_SPACE){
if(!isset($string{0})||!isset($key{0})){
returnfalse;
}

$dynKey=$isEncrypt?hash("sha1",microtime(true)):substr($string,0,40);
$fixedKey=hash("sha1",$key);

$dynKeyPart1=substr($dynKey,0,20);
$dynKeyPart2=substr($dynKey,20);
$fixedKeyPart1=substr($fixedKey,0,20);
$fixedKeyPart2=substr($fixedKey,20);
$key=hash("sha1",$dynKeyPart1.$fixedKeyPart1.$dynKeyPart2.$fixedKeyPart2);

$string=$isEncrypt?$fixedKeyPart1.$string.$dynKeyPart2:(isset($string{339})?gzuncompress(base64_decode(substr($string,40))):base64_decode(substr($string,40)));

$n=0;
$result="";
$len=strlen($string);

for($n=0;$n<$len;$n++){
$result.=chr(ord($string{$n})^ord($key{$n%40}));
}
return$isEncrypt?$dynKey.str_replace("=","",base64_encode($n>299?gzcompress($result):$result)):substr($result,20,-20);
}