PHP converts a numeric ID to a letter ID

The following is a detailed analysis of the implementation code for converting the digit ID to the letter ID using PHP. if you need a friend, you can refer to the ID that is frequently used on the website, it is generally a number, but we find that many of the current website IDs are letters, such as the video playback page of YouTube. its URL is similar to/watch? V = yzNjIBEdyww. The following is a method for generating letter IDs.
Example:

The code is as follows:

AlphaID (12354); // converts a number to a letter.
AlphaID ('ppqxn7cof', true); // converts the letter ID to a corresponding number.
AlphaID (12354, false, 6); // specify that the length of the generated letter ID is 6.

Source code:

The code is as follows:

/**
* Translates a number to a short alhanumeric version
*
* Translate 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 -- & gt; 9007199254740989
*
* This function is based on any2dec & dec2any
* Fragmer [at] mail [dot] ru
* See: http://nl3.php.net/manual/en/function.base-convert.php#52450
*
* If you want the alphaID to be at least 3 letter long, use
* $ 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.
* // First 26 directories already occupy 26 main levels
*
* More info on limitation:
*-Http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/165372
*
* If you really need this for bigger numbers you probably have to look
* At things like: http://theserverpages.com/php/manual/en/ref.bc.php
* Or: http://theserverpages.com/php/manual/en/ref.gmp.php
* 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 (http://kevin.vanzonneveld.net)
* @ License http://www.opensource.org/licenses/bsd-license.php New BSD Licence
* @ Version SVN: Release: $ Id: alphaID. inc. php 344 17: 43: 59Z kevin $
* @ Link http://kevin.vanzonneveld.net/
*
* @ 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
// ID short-and not so much secure,
// With this patch by Simon Franz (http://blog.snaky.org /)
// 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) <strlen ($ index ))
? Hash ('sha512', $ passKey)
: $ Passhash;

For ($ n = 0; $ n <strlen ($ index); $ n ++ ){
$ P [] = substr ($ passhash, $ n, 1 );
}

Array_multisort ($ p, SORT_DESC, $ I );
$ Index = implode ($ I );
}

$ Base = strlen ($ index );

If ($ to_num ){
// Digital number <-- alphabet letter code
$ In = strrev ($ in );
$ Out = 0;
$ Len = strlen ($ in)-1;
For ($ t = 0; $ t <= $ len; $ 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;
}