# Introduction

Zend_Config is designed to simplify the access to, and the use of, configuration data within applications. It provides a nested object property based user interface for accessing this configuration data within application code. The configuration data may come from a variety of media supporting hierarchical data storage. Currently Zend_Config provides adapters for configuration data that are stored in text files with Zend_Config_Ini and Zend_Config_Xml.

Using Zend_Config

Normally it is expected that users would use one of the adapter classes such as Zend_Config_Ini or Zend_Config_Xml, but if configuration data are available in a PHP array, one may simply pass the data to the Zend_Config constructor in order to utilize a simple object-oriented interface:

    // Given an array of configuration data
    $configArray = array(
        'webhost'  => 'www.example.com',
        'database' => array(
            'adapter' => 'pdo_mysql',
            'params'  => array(
                'host'     => 'db.example.com',
                'username' => 'dbuser',
                'password' => 'secret',
                'dbname'   => 'mydatabase'
            )
        )
    );

    // Create the object-oriented wrapper upon the configuration data
    $config = new Zend_Config($configArray);

    // Print a configuration datum (results in 'www.example.com')
    echo $config->webhost;

    // Use the configuration data to connect to the database
    $db = Zend_Db::factory($config->database->adapter,
                           $config->database->params->toArray());

    // Alternative usage: simply pass the Zend_Config object.
    // The Zend_Db factory knows how to interpret it.
    $db = Zend_Db::factory($config->database);

As illustrated in the example above, Zend_Config provides nested object property syntax to access configuration data passed to its constructor.

Along with the object oriented access to the data values, Zend_Config also has get() which will return the supplied default value if the data element doesn't exist. For example:

    $host = $config->database->get('host', 'localhost');

Using Zend_Config with a PHP Configuration File

It is often desirable to use a pure PHP-based configuration file. The following code illustrates how easily this can be accomplished:

    // config.php
    return array(
        'webhost'  => 'www.example.com',
        'database' => array(
            'adapter' => 'pdo_mysql',
            'params'  => array(
                'host'     => 'db.example.com',
                'username' => 'dbuser',
                'password' => 'secret',
                'dbname'   => 'mydatabase'
            )
        )
    );

    // Configuration consumption
    $config = new Zend_Config(require 'config.php');

    // Print a configuration datum (results in 'www.example.com')
    echo $config->webhost;