CodeIgniter Interview Questions and Answers

It is a globally available methods or functions that returns the Controller super-object which contains all the currently loaded classes. get_instance() function  returns the Controller class instance.

It is the process of taking a URI endpoint and decomposing it into parameters to determine module controller and action of that controller should receive the request.

CodeIgniter has a userfriendly URI routing rule so that we can re-route URL easily . There is a one-to-one relationship between a URL string and its corresponding controller class and its methods.

Routing is a technique through which we can converts SEO friendly URLs into a server code format that easily understandable.

We can manage these from routes.php file at the located in application/config.

Codeigniter supports various hook points.

• post_controller_constructor
• pre_controller
• post_sytem
• pre_system
• cache_override
• display_override
• post_controller

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We can use an absolute path to resources to link images/CSS/JavaScript from a view in CodeIgniter.

For Example :

<link rel = "stylesheet" type = "text/css" href = "<?php echo base_url(); ?>css/responsive.css">
<script type = 'text/javascript' src = "<?php echo base_url(); ?>js/jquery.js"></script>

Inhibitor is an error handling class. It is using the native PHP functions like set_error_handler, set_exception_handler, register_shutdown_function to handle all error's like parse errors, exceptions, and fatal errors.

You can follow these given steps to remove index.php from URL in Codeigniter.

• Please open config.php and change from $config['index_page'] = "index.php" to $config['index_page'] = "";
• Update also from $config['uri_protocol'] ="AUTO"; to $config['uri_protocol'] = "REQUEST_URI";
• Put this code in your htaccess file
  RewriteEngine on
RewriteCond $1 !^(index\.php|resources|robots\.txt)
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php/$1 [L,QSA]

In codeIgniter CSRF token is a random generated value that changes with each HTTP request sent by webform. When the form is submitted by user then website checks this submitted CSRF token equals or not the saved in the session.

We can enable CSRF protection from config.php and update the following values

$config['csrf_protection'] = TRUE;
$config['csrf_token_name'] = 'csrf_test_name'; //The token name
$config['csrf_cookie_name'] = 'csrf_cookie_name'; //The cookie name
$config['csrf_expire'] = 7200; // It will expire after this given time.

You have to build a file with name application/core/Blog.php and declare your class with

Class Blog extends CI_Input {
      // Write your code here
}

Codeigniter provides a rich set of libraries, which indirectly increase the speed of developing an application. These Codeigniter system library is located in system/libraries.

In Codeigniter the library can be loaded with $this->load->library('class name');

If we want to load multiple libraries then we can use like $this->load->library(array('comment', 'blog'));

How to add values in session in Codeigniter

$_SESSION['username'] = 'bestinterviewquestion.com' // It can be use in core PHP
$this->session->set_userdata('username', 'bestinterviewquestion.com'); // It can be done in Codeigniter

We can pass array to store values in session in Codeigniter.

$array = array(
    'username' => 'bestinterviewquestion.com',
    'email' => '[email protected]',
    'url' => 'https://www.bestinterviewquestion.com'
);

$this->session->set_userdata($array);

How to remove values in session in Codeigniter

unset($_SESSION['username']); // It can be use in core PHP
$this->session->unset_userdata('username'); // It can be done in Codeigniter

If we want to remove more values from session then we can use like this

$this->session->unset_userdata($array);  // $array is defined above. It is an array with key & values.

How to get data from session in Codeigniter

$this->session->userdata('username'); // Here we will get username, if it is exists in session.