# Zend_Config_Yaml

## Overview

YAML is a recursive acronym meaning "YAML Ain't Markup Language", and is intended as a "human friendly data serialization standard for all programming languages." It is often used for application configuration.

`Zend_Config_Yaml` is a lightweight `Zend_Config` extension. It includes a parser capable of recognizing most common YAML syntax used for purposes of configuration, and allows specifying other parsers should you want more complex syntax (e.g., ext/syck, spyc, sfYaml, etc.).

## Quick Start

The following is a YAML version of a standard application configuration.

    production:
      phpSettings:
        display_startup_errors: false
        display_errors: false
      includePaths:
        library: APPLICATION_PATH/../library
      bootstrap:
        path: APPLICATION_PATH/Bootstrap.php
        class: "Bootstrap"
      appnamespace: "Application"
      resources:
        frontController:
          controllerDirectory: APPLICATION_PATH/controllers
          moduleDirectory: APPLICATION_PATH/modules
          params:
            displayExceptions: false
        modules:
        db:
          adapter: "pdo_sqlite"
          params:
            dbname: APPLICATION_PATH/../data/db/application.db
        layout:
          layoutPath: APPLICATION_PATH/layouts/scripts/

    staging:
      _extends: production

    testing:
      _extends: production
      phpSettings:
        display_startup_errors: true
        display_errors: true

    development:
      _extends: production
      phpSettings:
        display_startup_errors: true
        display_errors: true
      resources:
        frontController:
          params:
            displayExceptions: true

To utilize it, you simply instantiate `Zend_Config_Yaml`, pointing it to the location of this file and indicating the section of the file to load. By default, constant names found in values will be substituted with their appropriate values.

    $config = new Zend_Config_Yaml(
        APPLICATION_PATH . '/configs/application.yaml',
        APPLICATION_ENV
    );

Once instantiated, you use it as you would any other configuration object.

    $db = Zend_Db::factory($config->resources->db);

## Configuration Options

The following options may be passed as keys to the third, `$options` argument of the constructor.

### Zend_Config_Yaml Options

allow_modifications

  The default behavior of `Zend_Config` is to mark the object as immutable once loaded. Passing this flag with a boolean `true` will enable modifications to the object.

skip_extends

  By default, any time a section extends another, `Zend_Config` will merge the section with the section it extends. Speciying a boolean `true` value to this option will disable this feature, giving you only the configuration defined explicitly in that section.

ignore_constants

  By default, `Zend_Config_Yaml` will replace constant names found in values with the defined constant value. You map pass a boolean `true` to this option to disable this functionality.

yaml_decoder

  By default, `Zend_Config_Yaml` uses a built in decoder, `Zend_Config_Yaml::decode()`, to parse and process YAML files. You may specify an alternate callback to use in place of the built-in one using this option.

## Available Methods

`__construct` $yaml, $section = null, $options = false

  Constructor. `$yaml` should refer to a valid filesystem location containing a YAML configuration file. `$section`, if specified, indicates a specific section of the configuration file to use. `$options` is discussed in the options section.

`decode` $yaml

  Parses a YAML string into a PHP array.

`setIgnoreConstants` $flag

  This static function may be used to globally override the default settings for how constants found in YAML strings are handled. By default, constant names are replaced with the appropriate constant values; passing a boolean `true` value to this method will override that behavior. (You can override it per-instance via the `ignore_constants` option as well.)

`ignoreConstants`

  This static method gives you the current setting for the `ignore_constants` flag.

## Examples

### Using Zend_Config_Yaml with sfYaml

As noted in the options section, `Zend_Config_Yaml` allows you to specify an alternate YAML parser at instantiation.

sfYaml is a Symfony component that implements a complete YAML parser in PHP, and includes a number of additional features including the ability to parse PHP expressions embedded in the YAML. In this example, we use the `sfYaml::load()` method as our YAML decoder callback. (Note: this assumes that the `sfYaml` class is either already loaded or available via autoloading.)

    $config = new Zend_Config_Yaml(
        APPLICATION_PATH . '/configs/application.yaml',
        APPLICATION_ENV,
        array('yaml_decoder' => array('sfYaml', 'load'))
    );