PHP code encryption and decryption method_PHP tutorial

//$key = "This is supposed to be a secret key !!!"; 估计是密阴
$key="这是一个密阴";
function keyED($txt,$encrypt_key)
{
$encrypt_key = md5($encrypt_key);
$ctr=0;
$tmp = "";
for ($i=0;$i {
if ($ctr==strlen($encrypt_key)) $ctr=0;
$tmp.= substr($txt,$i,1) ^ substr($encrypt_key,$ctr,1);
$ctr ;
}
return $tmp;
}

function encrypt($txt,$key)
{
srand((double)microtime()*1000000);
$encrypt_key = md5(rand(0,32000));
$ctr=0;
$tmp = "";
for ($i=0;$i {
if ($ctr==strlen($encrypt_key)) $ctr=0;
$tmp.= substr($encrypt_key,$ctr,1) .
(substr($txt,$i,1) ^ substr($encrypt_key,$ctr,1));
$ctr ;
}
return keyED($tmp,$key);
}

function decrypt($txt,$key)
{
$txt = keyED($txt,$key);
$tmp = "";
for ($i=0;$i {
$md5 = substr($txt,$i,1);
$i ;
$tmp.= (substr($txt,$i,1) ^ $md5);
}
return $tmp;
}

$string = "需要加密的字符串，如密码等.";

// 开始加密 encrypt $string, and store it in $enc_text
$enc_text = encrypt($string,$key);

// 开始解密 decrypt the encrypted text $enc_text, and store it in $dec_text
$dec_text = decrypt($enc_text,$key);

print "原始字符串 : $string
n";
print "加密后字串 : $enc_text
n";
print "解密后字串 : $dec_text
n";
?>