Configuring config/database.php file using php script - codeigniter

Question

I have a script in my controller which is as follows:
if($this->db->query("CREATE DATABASE IF NOT EXISTS db_ecommerce"))
{
$sql=file_get_contents('./databse_backup/backup.sql');
foreach (explode(";\n", $sql) as $sql)
{
$sql = trim($sql);
//echo $sql.'<br/>============<br/>';
if($sql)
{
$this->db->query($sql);
}
}
}
It creates a database and then runs a backup sql file.
My issue is that we need to configure the config/database.php file beforehand.
First I want this script to run and after that the database.php file should be changed.
$db['default']['hostname'] = 'localhost';
$db['default']['username'] = 'username';
$db['default']['password'] = 'password';
$db['default']['database'] = 'db_name';
Since its now for localhost hence,
$db['default']['hostname'] = 'localhost';
$db['default']['username'] = 'root';
$db['default']['password'] = '';
$db['default']['database'] = 'db_name';

Answer 1

An approach would be to have 'template file' in your installation folder like:
ex. database.php
$active_group = 'default';
$active_record = TRUE;
$db['default']['hostname'] = '<?php echo $hostname;?>';
$db['default']['username'] = '<?php echo $username;?>';
$db['default']['password'] = '<?php echo $password;?>';
$db['default']['database'] = '<?php echo $database;?>';
$db['default']['dbdriver'] = 'mysql';
$db['default']['dbprefix'] = '<?php echo $prefix;?>';
$db['default']['pconnect'] = TRUE;
$db['default']['db_debug'] = TRUE;
$db['default']['cache_on'] = FALSE;
$db['default']['cachedir'] = '';
$db['default']['char_set'] = 'utf8';
$db['default']['dbcollat'] = 'utf8_general_ci';
$db['default']['swap_pre'] = '';
$db['default']['autoinit'] = TRUE;
$db['default']['stricton'] = FALSE;
and then you can get the values for db connection (from a form for example) and write the new file in your codeigniter application (application/config/database.php)
ex.
$settings['hostname'] = $this->input->post('hostname');
$settings['username'] = $this->input->post('username');
$settings['password'] = $this->input->post('password');
$settings['database'] = $this->input->post('database');
$settings['prefix'] = $this->input->post('prefix');
$file_contents = $this->load->view('templates/database', $settings, true);
write_file($_SERVER['DOCUMENT_ROOT'].'application/config/database.php', $file_contents);