php数字加密解密的程序

/**
* Created by PhpStorm.
* User: Administrator
* Date: 2016/11/1
* Time: 12:26
*/
/*把数字转换成字符对应解析
* @param mixed $in String or long input to translate
* @param boolean $to_num Reverses translation when true
* @param mixed $pad_up Number or boolean padds the result up to a specified length
* @param string $passKey Supplying a password makes it harder to calculate the original ID
*/
function alphaID($in, $to_num = false, $pad_up = false, $passKey = null)
{
$index = "abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
if ($passKey !== null) {
// Although this function's purpose is to just make the
// ID short - and not so much secure,
// with this patch by Simon Franz (http://blog.s*n**aky.org/)
// you can optionally supply a password to make it harder
// to calculate the corresponding numeric ID

for ($n = 0; $n $i[] = substr( $index,$n ,1);
}

$passhash = hash('sha256',$passKey);
$passhash = (strlen($passhash) ? hash('sha512',$passKey)
: $passhash;

for ($n=0; $n $p[] = substr($passhash, $n ,1);
}

array_multisort($p, SORT_DESC, $i);
$index = implode($i);
}

$base = strlen($index);

if ($to_num) {
// Digital number $in = strrev($in);
$out = 0;
$len = strlen($in) - 1;
for ($t = 0; $t $bcpow = bcpow($base, $len - $t);
$out = $out + strpos($index, substr($in, $t, 1)) * $bcpow;
}

if (is_numeric($pad_up)) {
$pad_up--;
if ($pad_up > 0) {
$out -= pow($base, $pad_up);
}
}
$out = sprintf('%F', $out);
$out = substr($out, 0, strpos($out, '.'));
} else {
// Digital number -->> alphabet letter code
if (is_numeric($pad_up)) {
$pad_up--;
if ($pad_up > 0) {
$in += pow($base, $pad_up);
}
}

$out = "";
for ($t = floor(log($in, $base)); $t >= 0; $t--) {
$bcp = bcpow($base, $t);
$a = floor($in / $bcp) % $base;
$out = $out . substr($index, $a, 1);
$in = $in - ($a * $bcp);
}
$out = strrev($out); // reverse
}

return $out;
}
$str = alphaID("1245");
echo $str."
";
echo alphaID($str,true);