Save and restore search parameters as unique ID

Noob question here. I'm overhauling some "Search" pages in a real estate website. I would like to be able to generate an unique ID (hash?) which contains in itself all the parameters of the search, e.g., the user would be given an URL in the form of http://search.example.com/a95kl53df-02, and loading this URL would repeat the exact same search.

Some of the search parameters are simply one of several options, some are integers, and there are also keywords (which I'll just append after the ID, I guess). What's the general approach to cramming this data into a string? I'm fairly comfortable with PHP/MySQL, but my practical experience is next to none, so I don't know "how it's done".

EDIT: I do not need the string to be random, and, indeed, I need the process to be two-way. Perhaps hash isn't the correct term, then. As for why - I'm doing this for the sake of brevity, since current URLs contain at least 22 G开发者_运维百科ET parameters.

I have the nasty habit of always asking my questions on the Interwebs a bit too early, reconsiderations popping right into my head as soon as I have posted. I'm currently drafting a possible solution. I'm still open to any suggestions, though.

Hashes are not unique

A hash is NOT unique, you can't use it. Any hash can result from an infinite number of given strings.

You don't need randomness, just a unique token

You should just generate a unique token with the help of the database (even just an autoindexed id). You can create a cronjob that deletes old searches after a while.

That table would minimally contain the unique token plus the original search string.

Possible implementation

• User does a search
• Search params are stored in database, token is returned
• Token is given to user in some way (e.g. do you want to save this search for later)
• When user wants to repeat search with token, search string is retrieved from db and search run

You could use something like mcrypt() on $_SERVER['QUERY_STRING'], and then decrypt it if an encrypted URL is passed in. However, there are all sorts of problems here and I recommend not doing that.

Based on your edit that you are doing this because of a complicated URL, I would suggest that hashing is going to make the problem worse. If you have an error with the URL, you now have multiple places it could be going wrong.

Just make a random key that you then lookup in a simple flat-file database. You could check whether the URL is already in the database and then return the key if it is.

Another advantage of this system is that if your URL structure changes, then you can change all the URLs in the database and the users' short URLs still work.

Well to be random (which by the way you never can be), you can hash let us say the microtime (which is random-sh, since there is a low possibility that 2 users will search at the same time) along with some salt, with what you can use is the query id:

so something like:

$store_unique = md5(microtime().$queryID);
//the $store_unique you can save to the db with the query params
//then when anyone goes to the random url, you can check it against the db

UPDATE

Due to the comments below, I offer another solution (which can be more unique):

$store_unique = microtime(). "-" .$queryID;
//the $store_unique you can save to the db with the query params
//then when anyone goes to the random url, you can check it against the db