This article was written in 2009. It might or it might not be outdated. And it could be that the layout breaks. If that’s the case please let me know.

Creating my own small URL generator

UPDATE: You probably shouldn’t use this script. Try another result in Google please.

This page is here only for archival purposes. You really shouldn’t use this

UPDATE: check out the extended version of this script: fitting URL.

Since I started twittering a few days ago, and Twitter allows just a few letters for each tweet, the need arose for a small URL generator, a service that replaces a long URL (like http://vasilis.nl/fotos/digitaal/kiki/kiki-2009/in-de-hangmat-05-09018.jpg/) with a small one (like http://vasilis.nl/a/6). I tried two services (tinyurl.com and tr.im) but both didn’t work as I wanted them to work, which is strange because I don’t want much. Fortunately I’m a nerd so I just wrote my own short URL service. I’ll explain what I did so you don’t have to figure out how to write your own. The other reason I write this blogpost is that I hope somebody will explain me if things can be done easier or more secure: I’m just googling for solutions, I’m no programmer. And I really hope that somebody with a math knob can help me count with the base 64 system I choose to use.

Here’s the code for people who rather read code than words.

Put the htacces file and a php file in a directory on your server, make sure that the htaccess file is writable (you probably don’t want it too writable though) and call the php file like this: http://example.com/a/tinyurl.php?tinyurl=http://www.verylongurl.com/

What does this code do? It reads the content of the .htaccess file, reads a commented number inside it, adds 1 to that number, assigns a unique letter/number combination to the URL you want to shorten, writes a redirect rule in htaccess-language and adds that to the original htaccess file. It gives back the new URL in a textfield with all text selected and focus on it. That’s all I want.

First check if a URL is given

<?php
$redirecturl = $_GET['tinyurl'];
if($redirecturl){

These symbols are allowed, 64 in total

$nummers = array('0','1','2','3','4','5','6','7','8','9','a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z','A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z','-','_');

Get the content of the .htacces file

$oldfile = file_get_contents('.htaccess');

By exploding on ‘#’ we get very usefull chunks of data

$aantallinks = explode('#', $oldfile);

$aantallinks[1] is the current number used for the math further on. We need to add 1 for that math

$numlinks = ($aantallinks[1]+1);

Here’s some math abracadabra. Hope somebody can make a less messier function out of it ⁽¹

if($numlinks>count($nummers)){
$aantalcijfers = floor($numlinks/count($nummers));
$tweedecijfer = ($numlinks-($aantalcijfers*count($nummers)));
$newurl = $nummers[$aantalcijfers].$nummers[$tweedecijfer];
}
else{
$newurl = $nummers[$aantallinks[1]];
}

The math blob ends here, I can get back to explaining

Here we start writing the new content for the .htacces file
First the coded number we need for the math blob:

$newfile = '#'.$numlinks.'#'."\n";

Next we write back the old redirects

$newfile.= $aantallinks[2]."\n";

Here’s the new redirect

$newfile.= 'Redirect 301 /a/'.$newurl.' '.$redirecturl;

And here we write the new content into the .htacces file

file_put_contents('.htaccess',$newfile);

Create the feedback HTML

echo '<input type="text" value="http://vasilis.nl/a/'.$newurl.'" id="deinput">';

Some script to select the new URL so you only need to copy it.

echo '<script type="text/javascript">document.getElementById("deinput").select();document.getElementById("deinput").focus();</script>';
}

Functional code ends here.
The script ends with a disfunctional else statement which makes sure nothing happens when nu URL is given

else{
}
?>


Now, in an empty .htacces file just write down this:

#0#


⁽¹ My programming and math skills end here. This math blob generates a url with one or two symbols, I don’t understand how to make it add an extra symbol if necessary (for instance after 64×64=4096 URL’s). In other words, I want http://vasilis.nl/a/__ to be followed by http://vasilis.nl/a/000 but I don’t know how to do it.