Encoding like base36 including uppercase - php

Question

I am using base36 to shorten URLs. I have an id of a blog entry and convert that id to base36 to make it smaller. Base36 only includes lowercase letters. How can I include uppercase letters? If I use base64_encode it actually makes the string longer.

Answer 1

you can find examples of source-code to create short-urls containing letters (both lower and upper case) and number on those two articles, for instance :
Create short IDs with PHP - Like Youtube or TinyURL
Building a URL Shortener
Here is the portion of code used in that second article (quoting) :
$codeset = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
$base = strlen($codeset);
$n = 300;
$converted = "";
while ($n > 0) {
$converted = substr($codeset, ($n % $base), 1) . $converted;
$n = floor($n/$base);
}
echo $converted; // 4Q
And you can pretty easily encapsulate this in a function -- only thing to consider is that $n is to be received as a parameter :
function shorten($n) {
$codeset = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
$base = strlen($codeset);
$converted = "";
while ($n > 0) {
$converted = substr($codeset, ($n % $base), 1) . $converted;
$n = floor($n/$base);
}
return $converted;
}
And calling it this way :
$id = 123456;
$url = shorten($id);
var_dump($url);
You get :
string 'w7e' (length=3)
(You can also add some other characters, if needed -- depending on what you want to get in your URLs)
Edit after the comment :
Reading through the second article (from which I got the shortening code), you'll find the code that does the un-shortening.
Encapsulating that code in a function shouldn't be that hard, and might get you something like this :
function unshorten($converted) {
$codeset = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
$base = strlen($codeset);
$c = 0;
for ($i = strlen($converted); $i; $i--) {
$c += strpos($codeset, substr($converted, (-1 * ( $i - strlen($converted) )),1))
* pow($base,$i-1);
}
return $c;
}
And calling it with a shortened-url :
$back_to_id = unshorten('w7e');
var_dump($back_to_id);
Will get you :
int 123456

Answer 2

function dec2any( $num, $base=62, $index=false ) {
// Parameters:
// $num - your decimal integer
// $base - base to which you wish to convert $num (leave it 0 if you are providing $index or omit if you're using default (62))
// $index - if you wish to use the default list of digits (0-1a-zA-Z), omit this option, otherwise provide a string (ex.: "zyxwvu")
if (! $base ) {
$base = strlen( $index );
} else if (! $index ) {
$index = substr( "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ" ,0 ,$base );
}
$out = "";
for ( $t = floor( log10( $num ) / log10( $base ) ); $t >= 0; $t-- ) {
$a = floor( $num / pow( $base, $t ) );
$out = $out . substr( $index, $a, 1 );
$num = $num - ( $a * pow( $base, $t ) );
}
return $out;
}
Shamelessly borrowed from a commenter on PHP's base_convert() page (base_convert() only works up to base 32).