So I'm finally going to rewrite my url shortener.. But I have some performance issues.. This is de function I use to generator a random code (short url) for a long url. This works fine. For now.. Each time when someone generates a code this is checked with the database if it doesn't exist yet, if it does, this process starts all over again until…

CodeGenerator.php

<?php
/**
 * @author: WouterDS
 * @created: 01/01/13, 22:28
 * @filename: CodeGenerator.php
 */
class CodeGenerator {
    public static function randomCode($length = 4, $codeset = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ") {
      $converted = '';

    	$codesetLength = strlen($codeset);

    	for($i = 0; $i < $length; $i++) {
    		$randomCharacter = substr($codeset, floor(rand(0, $codesetLength)), 1);
    		$converted .= $randomCharacter;
    	}

    	return $converted;
    }
}

You can "create" 62 positional numbering system (like hexadecimal is 16)
Then you can convert a auto increment value to the short value (and back)

It's not fully random but if you use the characters in a random order it can be pseudo random