<?php
/**
* 加密解密类
* 该算法仅支持加密数字。比较适用于数据库中id字段的加密解密，以及根据数字显示url的加密。
* @author 深秋的竹子
* @version alpha
* @加密原则 标记长度 + 补位 + 数字替换
* @加密步骤：
* 将a-z,A-Z,0-9 62个字符打乱，取前M(数字最大的位数)位作为 标记长度字符串，取第M+1 到第M+10位为数字替换字符串，剩余的为补位字符串
* 1.计算数字长度n,取乱码的第n位作为标记长度。
* 2.计算补位的长度，加密串的长度N -1 – n 为补位的长度。根据指定的算法得到补位字符串。
* 3.根据数字替换字符串替换数字，得到数字加密字符串。
* 标记长度字符 + 补位字符串 + 数字加密字符串 = 加密串
* Usage:
* $obj = new XDeode(9);
* $e_txt = $obj->encode(123);
* echo $e_txt.'<br/>’;
* echo $key->decode($e_txt);
*/
class XDeode{
private $strbase = “Flpvf70CsakVjqgeWUPXQxSyJizmNH6B1u3b8cAEKwTd54nRtZOMDhoG2YLrI”;
private $key,$length,$codelen,$codenums,$codeext;
function __construct($length = 9,$key = 2543.5415412812){
$this->key = $key;
$this->length = $length;
$this->codelen = substr($this->strbase,0,$this->length);
$this->codenums = substr($this->strbase,$this->length,10);
$this->codeext = substr($this->strbase,$this->length + 10);
}

function encode($nums){
$rtn = “”;
$numslen = strlen($nums);
//密文第一位标记数字的长度
$begin = substr($this->codelen,$numslen – 1,1);
//密文的扩展位
$extlen = $this->length – $numslen – 1;
$temp = str_replace(‘.’, ”, $nums / $this->key);
$temp = substr($temp,-$extlen);
$arrextTemp = str_split($this->codeext);
$arrext = str_split($temp);
foreach ($arrext as $v) {
$rtn .= $arrextTemp[$v];
}
$arrnumsTemp = str_split($this->codenums);
$arrnums = str_split($nums);
foreach ($arrnums as $v) {
$rtn .= $arrnumsTemp[$v];
}
return $begin.$rtn;
}

function decode($code){
$begin = substr($code,0,1);
$rtn = ”;
$len = strpos($this->codelen,$begin);
if($len!== false){
$len++;
$arrnums = str_split(substr($code,-$len));
foreach ($arrnums as $v) {
$rtn .= strpos($this->codenums,$v);
}
}

return $rtn;
}
}
/**** 示例 ****/
$begin = 9950;
$end = $begin + 50;
$obj = new XDeode(9);
for($i=$begin;$i<$end;$i++){
$en = $obj->encode($i);
$de = $obj->decode($en);
echoln(“[{$i}]=[{$en}]=[{$de}]”);
}
function echoln($str){
echo “{$str}<br/>”;
}
?>

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