Zend_Config Proposal for the Zend Framework

I posted a Zend Framework proposal for Zend_Config, obviously based on the work I’ve done so far for Akrabat_Config.

The main difference from the Akrabat_Config posted here is that I’ve split the class into Zend_Config_Abstract and Zend_Config_Ini so that it can easily be extended to support YAML or XML or whatever other config file formats there are.

The proposal is:

Zend Framework Component Proposal


Proposed Component Name
-----------------------------------------------
Zend_Config


Proposers
-----------------------------------------------
Rob Allen (rob@akrabat.com


Revision
-----------------------------------------------
1.0 - 18 April 2007: Initial submission


Overview
-----------------------------------------------
Zend_Config is a very simple configuration file reader.
It provides an easy means to read configuration files
and access the data within them as a set of key->value
pairs. It will support at least one nested level of data.
Initially providing support for ini files, it should
be easy to extend for other formats such as YAML.


References
-----------------------------------------------
Mailing list thread resurrected here:
    http://www.zend.com/lists/fw-general/200604/msg00178.html.
Unfortunately, I could not find the original post by Andi Gutmans in the archives.

Other discussion can be found here:
    http://www.akrabat.com/index.php?s=Akrabat_Config


Requirements
-----------------------------------------------
* Ability to load a single config file and provide access to the data
  as an array.
* Ability to load additional files which then override already loaded
  data.
* Optional load a single section from a config file.
* For ini files, optional support for a single level "namespace" using
  the syntax:
        namespace.property = value
* For ini files, support for including other sections within this
  section's key using the syntax:
        include = section


Dependencies on Other Framework Components
-----------------------------------------------
Zend_Exception


Theory of Operation
-----------------------------------------------
Akrabat_Config_Abstract provides common functionality for all concrete
implementations. It provides the standard retrieval functionality for
concrete classes and prevents programmatic setting of config values.

Akrabat_Config_Ini is a concrete implementation that loads ini files. It
can either load an entire ini file or just a single section. It is
possible to load multiple ini files in which case, values for
duplicate keys will override the previously loaded value. This is useful
to allow for overriding a common config file with context specific
data such as for a staging or test server.

Akrabat_Config_Ini also supports using the first "." in a key name to
provide an additional nesting level. That is a key named db.name will
be represented as $config['db']['name'].

Akrabat_Config_ini also supports loading of keys from one section of the
ini file into another section. This is done using a special key called
"include". This key takes a comma separated list of section names.

In the future, should there be demand for other config file types, a
Zend_Config class could be created at a later stage that has a factory
function that returns the correct concrete class based on the filename
of the config file supplied.  For example, myapp.ini would create and
return a Zend_Config_Ini object whereas myapp.yml would create and
return a Zend_Config_Yaml object.


Class Index
-----------------------------------------------
Zend_Config_Exception
Zend_Config_Abstract
Zend_Config_Ini


Use Cases
-----------------------------------------------
Given the following ini file:
    [all]
    namespace.property = example
    db.connection = foo
    db.name = bar
    hostname = www.zend.com

    [andi_development]
    include=all
    hostname=andi_box
    db.connection=localhost

    [staging]
    include=all
    hostname=dev.zend.com


Then we can do something like:

< ?php
    $obj=new Zend_Config("myapp.ini", "andi_development");
    print $obj->hostname;   // prints andi_box
    print $obj->db['connection']; // prints localhost
    print $obj->db['name']; // prints bar
?>

Alternatively we can do:
< ?php
    $obj=new Zend_Config("myapp.ini");
    print $obj->andi_development['hostname'];   // prints andi_box
    print $obj->andi_development['db']['connection']; // prints localhost
    print $obj->andi_development['db']['name']; // prints bar
?>


Given a config file containing:
    [db]
    adapter = pdoMysql
    config.host = localhost
    config.username = akrabat
    config.password = 123456
    config.dbname = atasks

We can do:
< ?php
    $obj = new Zend_Config('myapp.ini');
    $db = Zend_Db::factory($obj->db['adapter'], $obj->db['config']);
?>


Class Skeletons
-----------------------------------------------
class Zend_Config_Exception extends Zend_Exception {}

class Zend_Config_Abstract
{
    protected $_config;

    function __construct($filename=null, $section=null) {}

    /**
     * Load a config file, overwriting any duplicate keys.
     * If $section is null, then the entire file is loaded.
     *
     * @param string $filename
     * @param string $section
     */
    abstract public function load($filename, $section=null);

    /**
     * Retreive a value from the config key called $name
     *
     * @param string $name
     * @param mixed $default
     * @return mixed
     */
    public function get($name, $default=false) {}

    /**
     * Does the config key $name exist?
     *
     * @param string $name
     * @return boolean
     */
    public function exists($name) {}

    /**
     * magic function so that $obj->value will work.
     *
     * @param string $name
     * @return mixed
     */
    public function __get($name) {}

    /**
     * This is a read only class... throw an exception on
     * setting a key!
     *
     * @param string $name
     * @param mixed $value
     */
    public function __set($name, $value) {}

}


class Zend_Config_Ini extends Zend_Config_Abstract
{
    /**
     * Load a config file, overwriting any duplicate keys.
     * If $section is null, then the entire file is loaded.
     *
     * @param string $filename
     * @param string $section
     */
    public function load($filename, $section=null) {}

    /**
     * Helper function to process the "include=" inheritance and then
     * process the "dot" single level sub-array syntax in each key.
     *
     * @param array $iniArray
     * @param string $section
     * @return array
     */
    protected function processIncludes($iniArray, $section) {}

    /**
     * Helper function to handle single level namespace in the key.
     * Uses the first "." as the separator.
     *
     * @param array $section
     * @return array
     */
    protected function processLevelsInSection($section) {}

}