Theory of Operation¶
Configuration data are made accessible to
Zend\Config\Config‘s constructor with an associative array,
which may be multi-dimensional, so data can be organized from general to specific. Concrete adapter
classes adapt configuration data from storage to produce the associative array for
constructor. If needed, user scripts may provide such arrays directly to
Zend\Config\Config‘s constructor, without using
a reader class.
Each value in the configuration data array becomes a property of the
Zend\Config\Config object. The key is used as the
property name. If a value is itself an array, then the resulting object property is created as a new
Zend\Config\Config object, loaded with the array data. This occurs recursively, such that a hierarchy of
configuration data may be created with any number of levels.
Zend\Config\Config implements the Countable and Iterator interfaces in order to facilitate simple
access to configuration data. Thus,
Zend\Config\Config objects support the count() function and
PHP constructs such as foreach.
By default, configuration data made available through
Zend\Config\Config are read-only, and an assignment
$config->database->host = 'example.com';) results in a thrown exception. This default behavior may be
overridden through the constructor, allowing modification of data values. Also, when modifications are
Zend\Config\Config supports unsetting of values (i.e.
isReadOnly() method can be used to determine if modifications to a given
Zend\Config\Config object are
allowed and the
setReadOnly() method can be used to stop any further modifications to a
object that was created allowing modifications.
Modifying Config does not save changes
It is important not to confuse such in-memory modifications with saving configuration data out to specific
storage media. Tools for creating and modifying configuration data for various storage media are out of scope
with respect to
Zend\Config\Config. Third-party open source solutions are readily available for the purpose
of creating and modifying configuration data for various storage media.
If you have two
Zend\Config\Config objects, you can merge them into a single object using the
function. For example, given
$localConfig, you can merge data from
$config->merge($localConfig);. The items in
$localConfig will override any items with the
same name in
Zend\Config\Config object that is performing the merge must have been constructed to allow
modifications, by passing
TRUE as the second parameter of the constructor. The
setReadOnly() method can
then be used to prevent any further modifications after the merge is complete.