Schema based configuration registry

This API provides configuration settings management for PHP applications.

It provides two components:

• Interfaces for reading and writing configuration in very simple and efficient manner.

• A full API for reading and browsing the configuration schema, allowing to manage your configuration in the same way as the Windows registry or the GSettings API.

It also gives:

• A very simple interface for writing storage backend easily.

• A less but still very simple interface for writing your schema browser implementation easily.

• A fully working configuration cursor implementation that uses any storage backend and any schema browser backend.

• A fully working storage backend proxy that caches read keys based upon two simple callables: a cache setter and a cache getter for working; Allowing you to easily add a cache layer for configuration.

Main features:

• Every value is identified by a path, e.g. a/b/c.

• Every value is typed using a primitive type or a list or hashmap of primitive types.

• All paths together give a single tree in which the full configuration values can be read and written.

• All path may be defined in a schema. Schema allows tree introspection.

• Error control on read/write operations which disallows mistyping values.

• Can be used with a schema: everything is stricly typed

• Can be used without a schema: just plug-in any storage, loose the introspection capabilities, but keep the storage plugability and the ArrayAccess syntaxic sugar

Getting started

Cursor basic usage

The following example will show you how to set and get values from a configuration cursor. Note that a configuration backend is nothing more than a cursor which is considered as being the root of the configuration tree.

For example, consider the following config.ini file:

; My application configuration
foo = bar

[a]
foo = baz

And the following sample code:

// You have to start with something
$config = new MemoryBackend(
    parse_ini_file("config.ini", true));

// Simple read operation
if ($config['a/b/c']) {
    do_something();
}

// Next 2 will echo "bar"
echo $config['foo'];
echo $config['/foo'];

// Next 2 will echo "baz"
echo $config['a/foo'];

// Set a value (schema less if unknown)
$config['a/b/c'] = 42;

// Get a sub tree cursor
$cursor = $config->getCursor('a/b');
// Works with relative path, this echoes 42
echo $cursor['c'];

Instanciating a full configuration stack

If you are building a complex application that needs a full stack configuration API, including configuration keys typing and introspection abilities, follow the next example.

// Create your schema and storage instances, could be anything
// else including your own implementation
$schema = new MemoryWritableSchema();
$storage = new MemoryStorage();
$root = null;

// Optional set, we could use a caching proxy
$cacheId = $__SERVER['REQUEST_URI'];
$storage = new CacheStorageProxy(
    $storage,
    function () use ($cacheId) {
        return apc_fetch($cacheId);
    },
    function ($data) use ($cacheId {
        apc_store($cacheId, $data);
    });

// Optionnaly, we could consider share the storage backend with
// multiple applications, case in which we need to namespace them
$root = '/my/application';

$cursor = new StoredBackend($storage, $schema, $root);

From this point, the $cursor variable is read to be used. As explained upper, this cursor is also the backend. You can from this point store a pointer to the $cursor backend anywhere, as in example a dependency injection container, and use it in your application.

Consider this example (using a Symfony DIC interface):

$container->set('config', $cursor);

// Later, considering we're now in a specific ContainerAware object
// context
$config = $this->getContainer()->get('config');

// If you want to read configuration
$value = $config['/some/path'];

// If you want to introspect schema
$schema = $config->getSchema();

The cursor is a single point of entry for the full API.

Basic configuration stack usage

@todo

History

Just commiting this code somewhere I can keep it.

I made this code a while ago, I just needed to see it back for some reason.

I won't lie, this is unfinished. The main goal was to plug it on GConf for a specific PHP application. Still doable, using php-dbus (search DBus in PECL site). I may do it some day that's something I'd be terribly curious to benchmark.