通常我们都会选择MD5的方法加密，但这种加密是不可逆的。往往我们开发程序时希望加密后可以再解密，但解密的方法是唯一的。于是我们预设一个唯一的字符映射表，通过这个映射把所有的字符替换调，以达到加密的效果。
代码段如下：
//获得随机唯一数组，页面打印后，替换md_str里的$hx_arr数组
$hx_arr = array(
'a'=>'s',
'b'=>'s',
'c'=>'s',
'd'=>'s',
'e'=>'s',
'f'=>'s',
'g'=>'s',
'h'=>'s',
'i'=>'s',
'j'=>'s',
'k'=>'s',
'l'=>'s',
'm'=>'s',
'n'=>'s',
'o'=>'s',
'p'=>'s',
'q'=>'s',
'r'=>'s',
's'=>'s',
't'=>'s',
'u'=>'s',
'v'=>'s',
'w'=>'s',
'x'=>'s',
'y'=>'s',
'z'=>'s',
'A'=>'s',
'B'=>'s',
'C'=>'s',
'D'=>'s',
'E'=>'s',
'F'=>'s',
'G'=>'s',
'H'=>'s',
'I'=>'s',
'J'=>'s',
'K'=>'s',
'L'=>'s',
'M'=>'s',
'N'=>'s',
'O'=>'s',
'P'=>'s',
'Q'=>'s',
'R'=>'s',
'S'=>'s',
'T'=>'s',
'U'=>'s',
'V'=>'s',
'W'=>'s',
'X'=>'s',
'Y'=>'s',
'Z'=>'s',
'0'=>'s',
'1'=>'s',
'2'=>'s',
'3'=>'s',
'4'=>'s',
'5'=>'s',
'6'=>'s',
'7'=>'s',
'8'=>'s',
'9'=>'s'
);
$t = array_keys($hx_arr);
$tt = $t;
foreach($tt as $k=>$v){
$r = array_rand($t);
$hx_arr[$v] = $t[$r];
unset($t[$r]);
}
print_r($hx_arr);
function md_str($temp_cookie,$md=0){
$hx_arr=array(
'a' => 'R',
'b' => '5',
'c' => 'r',
'd' => 'P',
'e' => 'g',
'f' => '6',
'g' => '8',
'h' => 'Z',
'i' => 'b',
'j' => 'l',
'k' => 'z',
'l' => 'x',
'm' => 'D',
'n' => '0',
'o' => '2',
'p' => '3',
'q' => 'j',
'r' => 'C',
's' => 'i',
't' => '9',
'u' => 'A',
'v' => 'N',
'w' => 'Y',
'x' => 'I',
'y' => 'S',
'z' => 'f',
'A' => 't',
'B' => 'J',
'C' => 'E',
'D' => 'e',
'E' => 'n',
'F' => 'y',
'G' => 'q',
'H' => 'B',
'I' => 'u',
'J' => 'K',
'K' => 'H',
'L' => 'o',
'M' => 'U',
'N' => 'L',
'O' => 'c',
'P' => '4',
'Q' => 'W',
'R' => 'k',
'S' => '7',
'T' => 's',
'U' => 'Q',
'V' => 'm',
'W' => 'p',
'X' => 'd',
'Y' => 'w',
'Z' => 'X',
'0' => 'F',
'1' => 'h',
'2' => 'v',
'3' => 'T',
'4' => 'G',
'5' => 'O',
'6' => '1',
'7' => 'V',
'8' => 'a',
'9' => 'M',
'='=>'@'
);
$t_arr_v='';
if($md== 0){
$t_cookie=base64_encode($temp_cookie);
$t_cookie_len=strlen($t_cookie);
for($i=0;$i<$t_cookie_len;$i++){
$t_arr_k=substr($t_cookie,$i,1);
$hx_arr[$t_arr_k] == '' && $hx_arr[$t_arr_k] = $t_arr_k;
$t_arr_v.=$hx_arr[$t_arr_k];
}
}elseif($md== 1){
$t_cookie_len=strlen($temp_cookie);
for($i=0;$i<$t_cookie_len;$i++){
$t_arr_k=substr($temp_cookie,$i,1);
$s_k = array_search($t_arr_k,$hx_arr);
$s_k = (string)$s_k;
$s_k == '' && $s_k = $t_arr_k;
$t_arr_v .= $s_k;
}
$t_arr_v=base64_decode($t_arr_v);
}else{
exit('error md cookie');
}
return$t_arr_v;
}
//测试部分
$a = '测试验证数据ABC789';
echo $a;
$b = md_str($a);
echo $b;
$c = md_str($b,1);
echo $c;