# Zend_Config_Writer

`Zend_Config_Writer` gives you the ability to write config files out of `Zend_Config` objects. It works with an adapter-less system and thus is very easy to use. By default `Zend_Config_Writer` ships with three adapters, which all work the same. You instantiate a writer with specific options, which can be filename and config. Then you call the `write()` method of the writer and the config file is created. You can also give `$filename` and `$config` directly to the `write()` method. Currently the following writers are shipped with `Zend_Config_Writer`:

- `Zend_Config_Writer_Array`

- `Zend_Config_Writer_Ini`

- `Zend_Config_Writer_Xml`

As an exception, `Zend_Config_Writer_Ini` has an additional option parameter nestSeparator, which defines with which character the single nodes are separated. The default is a single dot, like it is accepted by `Zend_Config_Ini` by default.

When modifying or creating a `Zend_Config` object, there are some things to know. To create or modify a value, you simply say set the parameter of the `Zend_Config` object via the parameter accessor (->). To create a section in the root or to create a branch, you just create a new array ("`$config->branch = array();`"). To define which section extends another one, you call the `setExtend()` method on the root `Zend_Config` object.

## Using Zend_Config_Writer

This example illustrates the basic use of `Zend_Config_Writer_Xml` to create a new config file:

    // Create the config object
    $config = new Zend_Config(array(), true);
    $config->production = array();
    $config->staging    = array();

    $config->setExtend('staging', 'production');

    $config->production->db = array();
    $config->production->db->hostname = 'localhost';
    $config->production->db->username = 'production';

    $config->staging->db = array();
    $config->staging->db->username = 'staging';

    // Write the config file in one of the following ways:
    // a)
    $writer = new Zend_Config_Writer_Xml(array('config'   => $config,
                                               'filename' => 'config.xml'));
    $writer->write();

    // b)
    $writer = new Zend_Config_Writer_Xml();
    $writer->setConfig($config)
           ->setFilename('config.xml')
           ->write();

    // c)
    $writer = new Zend_Config_Writer_Xml();
    $writer->write('config.xml', $config);

This will create an XML config file with the sections production and staging, where staging extends production.

## Modifying an Existing Config

This example demonstrates how to edit an existing config file.

    // Load all sections from an existing config file, while skipping the extends.
    $config = new Zend_Config_Ini('config.ini',
                                  null,
                                  array('skipExtends'        => true,
                                        'allowModifications' => true));

    // Modify a value
    $config->production->hostname = 'foobar';

    // Write the config file
    $writer = new Zend_Config_Writer_Ini(array('config'   => $config,
                                               'filename' => 'config.ini'));
    $writer->write();

## Loading a Config File

When loading an existing config file for modifications it is very important to load all sections and to skip the extends, so that no values are merged. This is done by giving the skipExtends as option to the constructor.