configuration


CakePHP: Storing Configs in your DB

There are many situations in web apps where site-wide configurations need to be accessible to users through admin interfaces, rather than configuration files residing on the server. It is a practical method of storing configuration values that may need changing from time to time, but without access to the core configuration file.

UPDATE (2008-10-22): This article has been published to the CakePHP Bakery

Code

Settings are stored in the database, so we will first need to start by creating the table:
CREATE TABLE settings (
id int(10) unsigned NOT NULL auto_increment,
key varchar(48) NOT NULL,
value text,
PRIMARY KEY  (id),
UNIQUE KEY key (key)
)

Next, go ahead and bake your model and controller, but don’t worry about baking-in some of the pre-built methods. Modify your model to look like this:

class Setting extends AppModel {

var $name = ‘Setting’;
var $key = ‘MyApp’;

//retrieve configuration data from the DB
function getcfg(){
$key=$this->key;
$cfgs = $this->find(‘first’,array(‘fields’=>array(‘id’,’key’,’value’)));

if (count($cfgs)) {
$this->checksum=$cfgs[‘Setting’][‘value’];
$cfgVal = unserialize($cfgs[‘Setting’][‘value’]);

}
Configure::write($key,$cfgVal);
}

//write configuration data back to the DB
function writecfg(){
$key = $this->key;

$rev = Configure::read($key);

$value=serialize($rev);

//if the configs haven’t changed, no need to save them
if ($value==$this->checksum) return;

//otherwise the configs have changed, so

$this->data = array(‘key’=>$key,’value’=>$value);

if ($setting = $this->findByKey($key)) {
$this->data[‘id’] = $setting[‘Setting’][‘id’];
}

$this->save($this->data);
}
}

You’ll notice that Configure:: values are serialized and stored together using the MyApp Configure::key. At first this may seem somewhat counter intuitive to how we think we should store configurations. However, consider the hassle involved with trying to figure out how/where to store multi-dimensional arrays in an inherently flat storage system (db). It’s probably doable, but not without considerable headaches. Storing everything in a serialized string allows Cake to worry about creating the structure – we just save the output.

Next, open up your app_controller.php file and add the following code to the top of the class:
var $uses = array('Setting');

You will also need to add some code to your AppController beforeFilter() and afterFilter() methods:

class AppController extends Controller {

var $uses = array(‘Setting’);

function beforeFilter(){
//reads the site-wide config values from the DB and puts them through the Configure::write method
$this->Setting->getcfg();
}

function afterFilter(){
//retrieves the site-wide configurations from Configure::read($key) and puts it back into the db if new
$this->Setting->writecfg();
}
}

Usage

Any place you would like to store a Configure:: value in the database, you only need to use the $key specified in the model. If you don’t, the values will not get saved. An example would look something like:
<? Configure::write('MyApp.themeName','My Great Theme'); ?>

Since the retrieval code is run in the before filter, we can treat the Configure:: vars like any others in our app when we need to access them. To recall a value we would run something like:
<? $myVar = Configure::read('MyApp.themeName'); //returns 'My Great Theme' ?>

Next Steps

Because this is only a very simple way to store configuration data (one row for the entire app), there will likely be some desire to extend it. You may wish to segregate certain data into their own rows (perhaps individual plugins or components), which would only require some additional code to accept additional keys for read/write access. That, my friends, is a job for another tutorial.