<?php
/**
 * ID混淆算法
 */
class IdCrypt
{
  /**
   * 对整数id进行可逆混淆
   */
  public static function encodeId($id)
  {
    $sid = ($id & 0xff000000);
    $sid += ($id & 0x0000ff00) << 8;
    $sid += ($id & 0x00ff0000) >> 8;
    $sid += ($id & 0x0000000f) << 4;
    $sid += ($id & 0x000000f0) >> 4;
    $sid ^= 11184810;
    return $sid;
  }
  /**
   * 对通过encodeId混淆的id进行还原
   */
  public static function decodeId($sid)
  {
    if (!is_numeric($sid)) {
      return false;
    }
    $sid ^= 11184810;
    $id = ($sid & 0xff000000);
    $id += ($sid & 0x00ff0000) >> 8;
    $id += ($sid & 0x0000ff00) << 8;
    $id += ($sid & 0x000000f0) >> 4;
    $id += ($sid & 0x0000000f) << 4;
    return $id;
  }
}
$idstr = new IdCrypt();
echo $encodeid = $idstr->encodeId('12345678');
echo "<br/>";
echo $decodeid = $idstr->decodeId($encodeid);
?>