一组PHP可逆加密解密算法_PHP教程

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);
}<br /><br /><span>解密算法如下：</span>

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 $str;
}<br /><br /><span>上述加密解密的过程均需要用到一个加密密钥（即参数$key）。</span><br /><br />

$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;<br /><br /><br />