如何在CodeIgniter中有条件地加载配置文件？

I need to create something similar to the following within my CodeIgniter project: -

• my_config.php
• config_production.php
• config_development.php

Now, my_config.php will be autoloaded. From there, if it is production server, config_production.php will be loaded; else config_development.php will be loaded.

How should I go about executing this?

I've tried doing the following in my_config.php:

<?php
if(gethostbyaddr ("127.0.0.1") == 'hello.sabya'){
    $this->config->load('config_production');
} else {
    $this->config->load('config_development');
}
?>

It is not working as $this->config is not initialized. How can I achieve this?

Two options: You can try referencing the object with "$CI" instead of "$this":

$CI =& get_instance();    //do this only once in this file
$CI->config->load();  
$CI->whatever;

...which is the correct way to reference the CI object from the outside.

Or secondly, you could switch configs from within your config.php file:

<?php
if(gethostbyaddr ("127.0.0.1") == 'hello.sabya'){
    $config['base_url'] = "http://dev.example.com/";
} else {
    $config['base_url'] = "http://prod.example.com/";

}
?>

...etc. Load all the differences in between the two if/else blocks.

When do you need the config initialised by? - could you not define a hook to load up the correct configuration once everything else had been initialised but before the controller had executed?

I got it working like this: -

$ci = & get_instance();

if (gethostbyaddr ("127.0.0.1") == 'production.example.com') {
    //Load production configuration
    $ci->load->config('config_production');
} elseif(gethostbyaddr ("127.0.0.1") == 'staging.example.com') {
    //Load staging configuration
    $ci->load->config('config_staging');
} else {
    //Load development configuration
    $ci->load->config('config_development');
} 

I use this in my case. For index.php

switch ($_SERVER['SERVER_NAME']) {
case 'localhost':
    define('ENVIRONMENT', 'development');
    break;
case 'example.com':
    define('ENVIRONMENT', 'production');
    break;
default:
    define('ENVIRONMENT', 'production');
    break;
}

For base_url in application/config.php:

switch ($_SERVER['SERVER_NAME']) {
case 'localhost':
    $config['base_url'] = "http://localhost/my_app/";
    break;
case 'example.com':
    $config['base_url'] = "http://example.com/";
    break;
default:
    $config['base_url'] = "http://example.com/";
    break;
}

For database in application/database.php:

switch ($_SERVER['SERVER_NAME']) {
case 'localhost':
    $db['default']['username'] = 'root';
    $db['default']['password'] = '123456';
    break;
case 'example.com':
    $db['default']['username'] = 'user';
    $db['default']['password'] = 'pass';
    break;
default:
    $db['default']['username'] = 'user';
    $db['default']['password'] = 'pass';
    break;
}

Why not use environments? - http://codeigniter.com/user_guide/general/environments.html

Also the config files are just arrays. Why not just include it and merge it with the existing array? Or even better in index.php:

if (gethostbyaddr ("127.0.0.1") == 'production.example.com')
{
    include(APPPATH.'config/config_production.php');
}
elseif (gethostbyaddr ("127.0.0.1") == 'staging.example.com')
{
    include(APPPATH.'config/config_staging.php');   
}
else
{
    include(APPPATH.'config/config_development.php');
}

foreach ($config AS $key => $item)
{
    $assign_to_config[$key] = $item;
}

But the best way is using environments in my opinion.

As Eric mentioned use environments.

You may load different configuration files depending on the current environment.

To create an environment-specific configuration file, create or copy a configuration file in application/config/{ENVIRONMENT}/{FILENAME}.php

Note: CodeIgniter always tries to load the configuration files for the current environment first. If the file does not exist, the global config file (i.e., the one in application/config/) is loaded. This means you are not obligated to place all of your configuration files in an environment folder − only the files that change per environment.

Why implement logic, when it's already there? ;)

This is old and already has an accepted answer but I have come up with a solution that I think works well. As @Eric mentioned, the best way to do this is to use the built-in functionality of the environment variable to determine the config logic. The problem I had this this approach is that it requires maintianing a lot of redundant values and you'll often want a central default config that gets run for all environments and only envrionment-specific values replace the defaults.

Your folder structure should be:

/app/config/config.php
/app/config/development/config.php
/app/config/production/config.php

Then, in your environment-specific config files, use the following as a starting point:

<?php  if ( ! defined('BASEPATH')) exit('No direct script access allowed');

// Set the default values first, then we'll overwrite environmental-specific values
include(APPPATH . '/config/' . pathinfo(__FILE__, PATHINFO_BASENAME));

Using this as a starting point will let you do the exact same thing for database.php, etc. -- any /config/ file you want an environment specific version for without writing your own envrionment-loading logic that CI already provides.