id是网站中经常出现的，香港服务器租用，它一般是数字，但是我们发现现在的网站很多id都是字母了,比如youtube的视频播放页它的url类似/watch?v=yznjibedyww。 下面是一个生成字母id的方法。
使用示例：
复制代码 代码如下:
alphaid(12354）； //会将数字转换为字母。
alphaid('ppqxn7cof',true）；//会将字母id转换为对应的数字。
alphaid(12354,false,6）；//指定生成字母id的长度为6.
源码：
复制代码 代码如下:
ppqxn7cof
*
* specifiying the second argument true, it will
* translate back e.g.:
* ppqxn7cof --> 9007199254740989
*
* this function is based on any2dec && dec2any by
* fragmer[at]mail[dot]ru
* see: #52450
*
* if you want the alphaid to be at least 3 letter long, use the
* $pad_up = 3 argument
*
* in most cases this is better than totally random id generators
* because this can easily avoid duplicate id's.
* for example if you correlate the alpha id to an auto incrementing id
* in your database, you're done.
*
* the reverse is done because it makes it slightly more cryptic,
* but it also makes it easier to spread lots of ids in different
* directories on your filesystem. example:
* $part1 = substr($alpha_id,0,1);
* $part2 = substr($alpha_id,1,1);
* $part3 = substr($alpha_id,2,strlen($alpha_id));
* $destindir = /.$part1./.$part2./.$part3;
* // by reversing, directories are more evenly spread out. the
* // first 26 directories already occupy 26 main levels
*
* more info on limitation:
* -
*
* if you really need this for bigger numbers you probably have to look
* at things like:
* or:
* but i haven't really dugg into this. if you have more info on those
* matters feel free to leave a comment.
*
* @author kevin van zonneveld
* @author simon franz
* @author deadfish
* @copyright 2008 kevin van zonneveld ()
* @license new bsd licence
* @version svn: release: $id: alphaid.inc.php 344 2009-06-10 17:43:59z kevin $
* @link
*
* @param mixed $in string or long input to translate
* @param boolean $to_num reverses translation when true
* @param mixed $pad_up number or boolean padds the result up to a specified length
* @param string $passkey supplying a password makes it harder to calculate the original id
*
* @return mixed string or long
*/
function alphaid($in, $to_num = false, $pad_up = false, $passkey = null)
{
$index = abcdefghijklmnopqrstuvwxyz0123456789abcdefghijklmnopqrstuvwxyz;
if ($passkey !== null) {
// although this function's purpose is to just make the
// id short - and not so much secure,
// with this patch by simon franz ()
// you can optionally supply a password to make it harder
// to calculate the corresponding numeric id
for ($n = 0; $n $i[] = substr( $index,$n ,1);
}
$passhash = hash('sha256',$passkey);
$passhash = (strlen($passhash) ? hash('sha512',$passkey)
: $passhash;
for ($n=0; $n $p[] = substr($passhash, $n ,1);
}
array_multisort($p, sort_desc, $i);
$index = implode($i);
}
$base = strlen($index);
if ($to_num) {
// digital number $in = strrev($in);
$out = 0;
$len = strlen($in) - 1;
for ($t = 0; $t $bcpow = bcpow($base, $len - $t);
$out = $out + strpos($index, substr($in, $t, 1)) * $bcpow;
}
if (is_numeric($pad_up)) {
$pad_up--;
if ($pad_up > 0) {
$out -= pow($base, $pad_up);
}
}
$out = sprintf('%f', $out);
$out = substr($out, 0, strpos($out, '.'));
} else {
// digital number -->> alphabet letter code
if (is_numeric($pad_up)) {
$pad_up--;
if ($pad_up > 0) {
$in += pow($base, $pad_up);
}
}
$out = ;
for ($t = floor(log($in, $base)); $t >= 0; $t--) {
$bcp = bcpow($base, $t);
$a = floor($in / $bcp) % $base;
$out = $out . substr($index, $a, 1);
$in = $in - ($a * $bcp);
}
$out = strrev($out); // reverse
}
return $out;
}
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