php常用加密解密功能函数示例

//加密函数
function lock_url($txt,$key=‘www.jb51.net‘)
{
  $chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-=+";
  $nh = rand(0,64);
  $ch = $chars[$nh];
  $mdKey = md5($key.$ch);
  $mdKey = substr($mdKey,$nh%8, $nh%8+7);
  $txt = base64_encode($txt);
  $tmp = ‘‘;
  $i=0;$j=0;$k = 0;
  for ($i=0; $i<strlen($txt); $i++) {
    $k = $k == strlen($mdKey) ? 0 : $k;
    $j = ($nh+strpos($chars,$txt[$i])+ord($mdKey[$k++]))%64;
    $tmp .= $chars[$j];
  }
  return urlencode($ch.$tmp);
}
//解密函数
function unlock_url($txt,$key=‘www.jb51.net‘)
{
  $txt = urldecode($txt);
  $chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-=+";
  $ch = $txt[0];
  $nh = strpos($chars,$ch);
  $mdKey = md5($key.$ch);
  $mdKey = substr($mdKey,$nh%8, $nh%8+7);
  $txt = substr($txt,1);
  $tmp = ‘‘;
  $i=0;$j=0; $k = 0;
  for ($i=0; $i<strlen($txt); $i++) {
    $k = $k == strlen($mdKey) ? 0 : $k;
    $j = strpos($chars,$txt[$i])-$nh - ord($mdKey[$k++]);
    while ($j<0) $j+=64;
    $tmp .= $chars[$j];
  }
  return base64_decode($tmp);
}