Id 通常都是用数字，不巧的是只有10个数字来使用，所以如果你有很多的记录，id往往变得非常冗长。当然对于计算机来说无所谓，但我们更希望id尽可能短。所以我们如何能使id变短？我们可以利用字母让它们附加上数字。字母可以解决!
所以这里就有两个问题：
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如何使用PHP和MySQL创建独特的短 字符串 id？
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或如何创建id类似YouTube的方式，如yzNjIBEdyww？
我很久以前创建了这个函数。是时候和大家分享一下了。
多就是少 – “这就是数学”
字母有26个字母。这是一个已经超过10字数。如果我们还区分大写和小写字母,并添加数字,我们已经有(26 x 2 + 10)=62个选项我们可以使用，让它出现在我们的id中。
当然我们现在也可以添加其他特殊字符如：/ * & #，但是那些可能导致的URL上的一些问题。
因为大约有60+字符，让id变的更短，所以我们有更多的选择可以使数据在每个位置。
这就是因为网址必须做的更加短，就像youtube上看到的：
转化你的id
不同于数据库服务器，网络服务容易收录这样的字符，这样你就可以让做一个转换id和字符串,同时保持你的数据库的快速与数字(MySQL真正喜欢它们纯数字);
由此产生的字符串不是很难破译, 但它可以是一个非常不错的功能使url或目录结构更紧凑的和更重要。
所以基本上:
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当有人请求rLHWfKd
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alphaID()将其转换为999999999999
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你查找的记录id 999999999999在你的数据库
PHP方式
/** * Translates a number to a short alhanumeric version * * Translated any number up to 9007199254740992 * to a shorter version in letters e.g.: * 9007199254740989 --> 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. * * The following code block can be utilized by PEAR's Testing_DocTest * <code> * // Input // * $number_in = 2188847690240; * $alpha_in = "SpQXn7Cb"; * * // Execute // * $alpha_out = alphaID($number_in, false, 8); * $number_out = alphaID($alpha_in, true, 8); * * if ($number_in != $number_out) { * echo "Conversion failure, ".$alpha_in." returns ".$number_out." instead of the "; * echo "desired: ".$number_in."\n"; * } * if ($alpha_in != $alpha_out) { * echo "Conversion failure, ".$number_in." returns ".$alpha_out." instead of the "; * echo "desired: ".$alpha_in."\n"; * } * * // Show // * echo $number_out." => ".$alpha_out."\n"; * echo $alpha_in." => ".$number_out."\n"; * echo alphaID(238328, false)." => ".alphaID(alphaID(238328, false), true)."\n"; * * // expects: * // 2188847690240 => SpQXn7Cb * // SpQXn7Cb => 2188847690240 * // aaab => 238328 * * </code> * * @author Kevin van Zonneveld <kevin@vanzonneveld.net> * @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 reverse s 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, $pass_key = null){ $out = ''; $index = 'abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ'; $base = strlen($index); if ($pass_key !== null) { // Although this function's purpose is to just make the // ID short - and not so much secure, // with this patch by Simon Franz ( log .snaky.org/) // you can optionally supply a password to make it harder // to calculate the corresponding numeric ID for ($n = 0; $n < strlen($index); $n++) { $i[] = substr($index, $n, 1); } $pass_ hash = hash('sha256',$pass_key); $pass_hash = (strlen($pass_hash) < strlen($index) ? hash('sha512', $pass_key) : $pass_hash); for ($n = 0; $n < strlen($index); $n++) { $p[] = substr($pass_hash, $n, 1); } array_multisort($p, SORT_DESC, $i); $index = implode($i); } if ($to_num) { // Digital number <<-- alphabet letter code $len = strlen($in) - 1; for ($t = $len; $t >= 0; $t--) { $bcp = bcpow($base, $len - $t); $out = $out + strpos($index, substr($in, $t, 1)) * $bcp; } if (is_numeric($pad_up)) { $pad_up--; if ($pad_up > 0) { $out -= pow($base, $pad_up); } } } else { // Digital number -->> alphabet letter code if (is_numeric($pad_up)) { $pad_up--; if ($pad_up > 0) { $in += pow($base, $pad_up); } } for ($t = ($in != 0 ? floor(log($in, $base)) : 0); $t >= 0; $t--) { $bcp = bcpow($base, $t); $a = floor($in / $bcp) % $base; $out = $out . substr($index, $a, 1); $in = $in - ($a * $bcp); } } return $out;}
还有一个可选的第三个参数:$pad_up。这能使生成的alphaId至少X字符长。
你可以支持更多字符(使生成的alphaID甚至更小)通过添加和修改函数顶部的$index变量。
Javascript方式
/** * Javascript AlphabeticID class * (based on a script by Kevin van Zonneveld <kevin@vanzonneveld.net>) * * Author: Even Simon <even.simon@gmail.com> * * Description: Translates a numeric identifier into a short string and backwords. * * Usage: * var str = AlphabeticID.encode(9007199254740989); // str = 'fE2XnNGpF' * var id = AlphabeticID. decode ('fE2XnNGpF'); // id = 9007199254740989; **/var AlphabeticID = { index:'abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ', /** * [@function]( AlphabeticID.encode * [@description]( Encode a number into short string * [@param]( integer * [@return]( string **/ encode:function(_number){ if(' undefined ' == typeof _number){ return null; } else if('number' != typeof(_number)){ throw new Error('Wrong parameter type'); } var ret = ''; for(var i=Math.floor(Math.log(parseInt(_number))/Math.log(AlphabeticID.index.length));i>=0;i--){ ret = ret + AlphabeticID.index.substr((Math.floor(parseInt(_number) / AlphabeticID.bcpow(AlphabeticID.index.length, i)) % AlphabeticID.index.length),1); } return ret.reverse(); }, /** * [@function]( AlphabeticID.decode * [@description]( Decode a short string and return number * [@param]( string * [@return]( integer **/ decode:function(_string){ if('undefined' == typeof _string){ return null; } else if('string' != typeof _string){ throw new Error('Wrong parameter type'); } var str = _string.reverse(); var ret = 0; for(var i=0;i<=(str.length - 1);i++){ ret = ret + AlphabeticID.index.indexOf(str.substr(i,1)) * (AlphabeticID.bcpow(AlphabeticID.index.length, (str.length - 1) - i)); } return ret; }, /** * [@function]( AlphabeticID.bcpow * [@description]( Raise _a to the power _b * [@param]( float _a * [@param]( integer _b * [@return]( string **/ bcpow:function(_a, _b){ return Math.floor(Math.pow(parseFloat(_a), parseInt(_b))); }};/** * [@function]( String.reverse * [@description]( Reverse a string * [@return]( string **/String.prototype.reverse = function(){ return this.split('').reverse().join('');};
