Extending the CodeIgniter Database Utility Class

You’d like to take advantage of CodeIgniter’s built-in database backup function as described here…

http://www.codeigniter.com/user_guide/database/utilities.html#backup

As you can see, only the `mysql` PHP database extension is supported. However, since the `mysql` PHP database extension has been deprecated, maybe you’re using another PHP database extension like `mysqli` instead. Now the problem is that you can no longer use CodeIgniter’s built-in database backup function without getting this error…

Unsupported feature of the database platform you are using.

The error simply means that if you use any PHP database extension besides `mysql`, there is no function included within any of CodeIgniter’s database drivers’ utility file for doing the backup.

No problem, we’ll just “extend” CodeIgniter’s database class.

Wrong! As per documentation,

Note: The Database classes can not be extended or replaced with your own classes.

Despite this limitation, there is a workaround below that will not involve editing CodeIgniter’s core system files.

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Solution:
Instead, we’ll simply “extend” CodeIgniter’s Loader class. Within this custom Loader, we’ll only copy and slightly modify the `dbutil()` function. Study the function below and compare it to the original. I simply check for the existence of my custom utility driver file and load it in place of the default.

`application/core/MY_Loader.php` contains…

<?php class MY_Loader extends CI_Loader {

    public function dbutil()
    {
        // this function taken from CI v2.2.0
        // system/core/Loader.php
        // modified as indicated below

        if (! class_exists('CI_DB'))
        {
            $this->database();
        }

        $CI =& get_instance();

        // for backwards compatibility, load dbforge so we can extend dbutils off it
        // this use is deprecated and strongly discouraged
        $CI->load->dbforge();

        require_once(BASEPATH . 'database/DB_utility.php');

        // START custom >>

        // path of default db utility file
        $default_utility = BASEPATH . 'database/drivers/' . $CI->db->dbdriver . '/' . $CI->db->dbdriver . '_utility.php';

        // path of my custom db utility file
        $my_utility = APPPATH . 'libraries/MY_DB_' . $CI->db->dbdriver . '_utility.php';

        // set custom db utility file if it exists
        if (file_exists($my_utility))
        {
            $utility = $my_utility;
            $extend = 'MY_DB_';
        }
        else
        {
            $utility = $default_utility;
            $extend = 'CI_DB_';
        }

        // load db utility file
        require_once($utility);

        // set the class
        $class = $extend . $CI->db->dbdriver . '_utility';

        // << END custom

        $CI->dbutil = new $class();

    }

}

Now we need to find the database driver that we’re using. For `mysqli`, it should be located within `system/database/drivers/mysqli/mysqli_utility.php`. This file contains the `_backup()` function and you can see that it’s empty (“unsupported”).

Create an exact duplicate of this file; rename it `MY_DB_mysqli_utility.php` and place it here…

`application/libraries/MY_DB_mysqli_utility.php`

Everything within this file should remain the same as the original, except for the name of the `class` and the contents of the `_backup()` function…

<?php
    class MY_DB_mysqli_utility extends CI_DB_utility {
    
    // this code taken from CI v2.2.0
    // system/database/drivers/mysqli/mysqli_utility.php

    // everything in here is same as default mysqli_utility
    ....
    // EXCEPT the _backup() function contains my own code

    function _backup($params = array())
    {
        //  my custom working backup code
        ....

NOW you can put whatever code you see fit into this version of the `_backup()` function. I’m not going to tell you how to do this, but you could look inside of `system/database/drivers/mysql/mysql_utility.php` for some inspiration. You could also try the backup function suggested in this posting, which seems to be working.

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The advantages to my technique are as follows…

– Updating the CodeIgniter system files leaves this solution intact.
– Changing the `dbdriver` setting in `config/database.php` will simply cause a fallback to the selected database utility driver. This solution is specific to one particular database driver (`mysqli`).
– Removing the `MY_Loader.php` file causes a fallback to the default database utility driver.
– Removing the `MY_DB_mysqli_utility.php` file causes a fallback to the default database utility driver.
– Update any other database utility driver by changing `mysqli` where-ever appropriate.

Note: This solution was successfully performed using CodeIgniter v2.2.0.