bitfields tutorial

[Ken Iovino]

vBulletin uses what they call bitfields in there system. Basicly you can have multiple settings within one database field. Is there any tutorial out there to show how one can do such a thing to custom scripts?

I always notice..

$var = array(

        'can_do_this'  => 1,

        'can_do_that'  => 2,

        'can_try_this' => 4,

        'can_do_those' => 8

); 

But never fully understode whats going on. Whats this called and can you point me to any tutorials avaiable? Thanks!

[chris_fuel]

Ok, this explanation should do it:

http://www.zend.com/zend/spotlight/c...lery-wade2.php

basically, you take an integer with a certain bit length, and you flag on/off certain bits to indicate permissions/etc. This is done through the various php bitwise operators:

http://us3.php.net/manual/en/languag...rs.bitwise.php

This is mainly done to save storage space. Though some people find it hard to work with on the database level, as they have to reference back and forth between the db and PHP code, which, for a DB admin who doesn't deal with PHP much, that can be quite painful . That said, if you're the one dealing with both the DB and the code, it's all you. However, if you have a DB admin, be considerate .

[Ken Iovino]

I deal with everything, so this should do well for me. Thanks alot Chris!

/me starts to read away!

Edit:


This cartoon really helped alot. I want to post it here for other users.

source: http://www.litfuel.net/tutorials/bitwise.htm

[chris_fuel]

hahaha, what.. on.. earth... I am so bookmarking that, that's the greatest . Oh and btw, spiral is awesome ( at least I think that's where that character is from.. ).

[Ken Iovino]

I thought you might get a kick out of that.