Configuration data are made accessible to the
through an associative array, which may be multi-dimensional, in order to support
organizing the data from general to specific. Concrete adapter classes
adapt configuration data from storage to produce the associative array for the
Zend_Config constructor. User scripts may provide such arrays
directly to the
Zend_Config constructor, without using an adapter
class, since it may be appropriate to do so in certain situations.
Each configuration data array value becomes a property of the
Zend_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 object, loaded with the array data. This occurs
recursively, such that a hierarchy of configuration data may be created with any number of
Zend_Config implements the Countable and
Iterator interfaces in order to facilitate simple access to
configuration data. Thus, one may use the
function and PHP constructs such as
» foreach with
By default, configuration data made available through
read-only, and an assignment (e.g.,
$config->database->host = 'example.com';)
results in a thrown exception. This default behavior may be overridden through the
constructor, however, to allow modification of data values. Also, when modifications are
Zend_Config supports unsetting of values (i.e.
readOnly() method can be used to determine if modifications to a
Zend_Config object are allowed and the
setReadOnly() method can be used to stop any further modifications
Zend_Config object that was created allowing modifications.
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. Third-party open source solutions are readily available for the purpose of creating and modifying configuration data for various storage media.
Adapter classes inherit from the
Zend_Config class since they utilize
Zend_Config family of classes enables configuration data to be
organized into sections.
Zend_Config adapter objects may be loaded
with a single specified section, multiple specified sections, or all sections
(if none are specified).
Zend_Config adapter classes support a single inheritance model that
enables configuration data to be inherited from one section of configuration data
into another. This is provided in order to reduce or eliminate the need for
duplicating configuration data for different purposes. An inheriting section
may also override the values that it inherits through its parent section.
Like PHP class inheritance, a section may inherit from a parent section,
which may inherit from a grandparent section, and so on, but multiple inheritance
(i.e., section C inheriting directly from parent sections A and B) is not supported.
If you have two
Zend_Config objects, you can merge them into a single
object using the merge() function. For example, given
$config and $localConfig, you can merge data from
$localConfig to $config using
$config->merge($localConfig);. The items in
$localConfig will override any items with the same name in
Zend_Configobject 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.