Re: Unique random string

Maybe this may appear a stupid answer but... Why don't create a database table and use the auto_increment field as the first part of the unique id.. the second part could be a randomly generated string of x chars... You could do this for example.. (supposing MySql) $second_part_alias = $rndstr; // a random string of desired characters lenght $query = "insert into first_part_aliases_table values('','$second_part_alias')"; // then execute the query $result = mysql_query($query, $lnk); $first_part_alias = mysql_insert_id($lnk);// get last insert id $unique_alias = $first_part_alias . "-" . $second_part_alias; // with this you'll be absolutely sure that no duplicates will be generated // Note: of course you have to estimate how many users will you may have in the next decade... in order to generate a second_part string not too long that if concatenated with first part, generates a string longer than 15 chars.. Supposing in the next decade people on the earth will be not more than 20 Billions 20,000,000,000 is a 11 chars long string (without commas) you'll create a string of 3 chars to be concatenated or if you want to be sure the alias is 15 chars long you can get the first_part_alias lenght (that varies if users increment) and calculate the difference from 15, for the lenght of the string to be concatenated as the second part... A unique id with this method could be: $ID = 34467-dgjGyy // for user number 34467 hope to be useful... Nicola Delbono ----- Original Message ----- From: "William Ahern" <wahern@mailshell.com> To: <php-general@lists.php.net> Sent: Wednesday, June 28, 2000 1:34 AM Subject: [PHP] Unique random string > Any ideas on how I can generate a 'guaranteed' unique ascii string less than > 15 characters. > > It must be guaranteed unique across several independent > servers. > > Currently we are generating random short strings to create unique aliases for > email addresses. The only problem is that to guarantee uniqueness we keep a log > of previous strings and check to make sure we don't create duplicates (we cannot > rotate strings. They must be absolutely unqiue for the next decade or so). > > The optimal solution would be to generate strings that are truly unique and > hopefully random enough, w/o having to go through the process of checking for > duplicates. > > I'd use uniqid(), except that it is 32 characters (too long since users will > have to handle them sometimes) and the algorithm must be available to C, C++, > Perl, whatever. > > Any comments, suggestions or answers! ;) would be great. > > Please add my address to the reply as I am not subscribed to the list. > > TIA, > > Bill > > -- > PHP General Mailing List (http://www.php.net/) > To unsubscribe, e-mail: php-general-unsubscribe@lists.php.net > For additional commands, e-mail: php-general-help@lists.php.net > To contact the list administrators, e-mail: php-list-admin@lists.php.net > >