CodeIgniter User Guide Version 2.1.2

Connecting to your Database

There are two ways to connect to a database:

Automatically Connecting

The "auto connect" feature will load and instantiate the database class with every page load. To enable "auto connecting", add the word database to the library array, as indicated in the following file:

application/config/autoload.php

Manually Connecting

If only some of your pages require database connectivity you can manually connect to your database by adding this line of code in any function where it is needed, or in your class constructor to make the database available globally in that class.

$this->load->database();

If the above function does not contain any information in the first parameter it will connect to the group specified in your database config file. For most people, this is the preferred method of use.

Available Parameters

  1. The database connection values, passed either as an array or a DSN string.
  2. TRUE/FALSE (boolean). Whether to return the connection ID (see Connecting to Multiple Databases below).
  3. TRUE/FALSE (boolean). Whether to enable the Active Record class. Set to TRUE by default.

Manually Connecting to a Database

The first parameter of this function can optionally be used to specify a particular database group from your config file, or you can even submit connection values for a database that is not specified in your config file. Examples:

To choose a specific group from your config file you can do this:

$this->load->database('group_name');

Where group_name is the name of the connection group from your config file.

To connect manually to a desired database you can pass an array of values:

$config['hostname'] = "localhost";
$config['username'] = "myusername";
$config['password'] = "mypassword";
$config['database'] = "mydatabase";
$config['dbdriver'] = "mysql";
$config['dbprefix'] = "";
$config['pconnect'] = FALSE;
$config['db_debug'] = TRUE;
$config['cache_on'] = FALSE;
$config['cachedir'] = "";
$config['char_set'] = "utf8";
$config['dbcollat'] = "utf8_general_ci";

$this->load->database($config);

For information on each of these values please see the configuration page.

Or you can submit your database values as a Data Source Name. DSNs must have this prototype:

$dsn = 'dbdriver://username:password@hostname/database';

$this->load->database($dsn);

To override default config values when connecting with a DSN string, add the config variables as a query string.

$dsn = 'dbdriver://username:password@hostname/database?char_set=utf8&dbcollat=utf8_general_ci&cache_on=true&cachedir=/path/to/cache';

$this->load->database($dsn);

Connecting to Multiple Databases

If you need to connect to more than one database simultaneously you can do so as follows:

$DB1 = $this->load->database('group_one', TRUE);
$DB2 = $this->load->database('group_two', TRUE);

Note: Change the words "group_one" and "group_two" to the specific group names you are connecting to (or you can pass the connection values as indicated above).

By setting the second parameter to TRUE (boolean) the function will return the database object.

When you connect this way, you will use your object name to issue commands rather than the syntax used throughout this guide. In other words, rather than issuing commands with:

$this->db->query();
$this->db->result();
etc...

You will instead use:

$DB1->query();
$DB1->result();
etc...

Reconnecting / Keeping the Connection Alive

If the database server's idle timeout is exceeded while you're doing some heavy PHP lifting (processing an image, for instance), you should consider pinging the server by using the reconnect() method before sending further queries, which can gracefully keep the connection alive or re-establish it.

$this->db->reconnect();

Manually closing the Connection

While CodeIgniter intelligently takes care of closing your database connections, you can explicitly close the connection.

$this->db->close();