Codeigniter: loading up multiple databases

Codeigniter's documentation does offer some insight into how to connect to multiple databases, but I didn't find it satisfactory. It suggests that by passing a second parameter
to the loader allows it to return an object which may be then queried like the normal $this->db->query();. Thus:

$DB1 = $this->load->database('config1', TRUE); 
$DB2 = $this->load->database('config2', TRUE); 

$DB1->query();

For my purposes at least this wasn't satisfactory because:

• I had an existing codebase using the more conventional $this->db->query() which would then have to be refactored.
• It gave the ability to load up the database as needed, but not all the time as was the case with the previously autoloaded config.
• It didn't work, the databases loading order affected one another and conflicted if called within the same method.

Solution:

Turn persistent connections off when using multiple connections fixes the problem of connection conflicts:

$db['default']['pconnect'] = FALSE;

Although beware this will likely incur a performance penalty as the connection now needs to be reestablished to the database at every connection

My solution to load up the databases more permanently was to create a custom loader library which handles this and places the connections in the traditional CI object. In my case, I added this library to /applications/config/autoload.php in the appropriate section:

/**
  * A simple class which handles loading multiple-databases in codeigniter
  */

 class DatabaseLoader {

         public function __construct() {
                 $this->load();
         }

         /**
          * Load the databases and ignore the old ordinary CI loader which only allows one
          */
         public function load() {
                 $CI =& get_instance();

                 $CI->db = $CI->load->database('default', TRUE);
                 $CI->db2 = $CI->load->database('db2', TRUE);
         }