<?php

function encrypt($data, $key)

{

$key = md5($key);

$x = 0;

$len = strlen($data);

$l = strlen($key);

for ($i = 0; $i < $len; $i++) {

if ($x == $l) {

$x = 0;

}

$char .= $key{$x};

$x++;

}

for ($i = 0; $i < $len; $i++) {

$str .= chr(ord($data{$i}) + (ord($char{$i})) % 256);

}

return base64_encode($str);

}


function decrypt($data, $key)

{

$key = md5($key);

$x = 0;

$data = base64_decode($data);

$len = strlen($data);

$l = strlen($key);

for ($i = 0; $i < $len; $i++) {

if ($x == $l) {

$x = 0;

}

$char .= substr($key, $x, 1);

$x++;

}

for ($i = 0; $i < $len; $i++) {

if (ord(substr($data, $i, 1)) < ord(substr($char, $i, 1))) {

$str .= chr((ord(substr($data, $i, 1)) + 256) - ord(substr($char, $i, 1)));

} else {

$str .= chr(ord(substr($data, $i, 1)) - ord(substr($char, $i, 1)));

}

}

return $str;

}



$data = 'PHP加密解密算法'; // 被加密信息

$key = '123'; // 密钥

$encrypt = encrypt($data, $key);

$decrypt = decrypt($encrypt, $key);

echo $encrypt, "\n", $decrypt;