Check for Ajax request in CodeIgniter

You can use $this->input->is_ajax_request() from the input class:

if (!$this->input->is_ajax_request()) {   exit('No direct script access allowed');}

There is no need to add an if (!$this->input->is_ajax_request()) to every AJAX method if you use hooks (CI docs). This is based on Jorge's solution in here with a few slight improvements:

config/config.php

Enable CI hooks by changing the default value (from FALSE):

$config['enable_hooks'] = TRUE;

config/hooks.php

Add the following at the end:

$hook['post_controller_constructor'] = array(    'class' => 'Ajax_only',    'function' => 'show_404_on_illegal_ajax',    'filename' => 'Ajax_only.php',    'filepath' => 'hooks');

post_controller_constructor: called immediately after your controller is instantiated, but prior to any method calls happening

config/ajax_methods.php

Create a new config file with all the controllers and methods that should only be invoked when an AJAX request is made:

<?phpdefined('BASEPATH') OR exit('No direct script access allowed');/*|--------------------------------------------------------------------------| References to all AJAX controllers' methods or the controller itself|--------------------------------------------------------------------------|| Based on Jorge's solution: https://stackoverflow.com/a/43484330/6225838| Key: controller name| Possible values:| - array: method name as key and boolean as value (TRUE => IS_AJAX)| - boolean: TRUE if all the controller's methods are for AJAX requests|*/$config['welcome'] = [  'index' => FALSE, // or 0 -> this line can be removed (just for reference)  'ajax_request_method_1' => TRUE, // or 1  'ajax_request_method_2' => TRUE, // or 1];$config['ajax_troller'] = TRUE;

hooks/Ajax_only.php

Create the hook itself, which detects if the current controller and/or its methods are present on the new config file above. If so, it shows the 404 default page when the current request is not AJAX and the method/controller has a truthy value in the config:

<?phpdefined('BASEPATH') OR exit('No direct script access allowed');class Ajax_only {  public function __construct()  {    $this->CI = &get_instance();    $this->CI->config->load('ajax_methods');  }  public function show_404_on_illegal_ajax()  {    $fetched_troller_val = $this->CI->config->item(      $this->CI->router->fetch_class()    );    $fetched_method = $this->CI->router->fetch_method();    $is_ajax_method = is_array($fetched_troller_val) &&        // verify if the method's name is present        isset($fetched_troller_val[$fetched_method]) &&        // verify if the value is truthy        $fetched_troller_val[$fetched_method];    // if the controller is not in the config file then    // config->item() returned NULL    if($fetched_troller_val !== NULL &&        $this->CI->input->is_ajax_request() === FALSE  &&        ($fetched_troller_val === TRUE || $is_ajax_method)      ) {      show_404();    }  }}

if you want customize the requests from your codeigniter app, try this:You must create a hook named Ajax_only.php in application/hooks folder

class Ajax_only {    private $_controllers = [];    private $CI;    public function __construct() {        $this->CI =& get_instance();    }    public function eval_request() {        $controller = $this->CI->router->fetch_class();        $method = $this->CI->router->fetch_method();        if ( array_key_exists( $controller, $this->_controllers ) && $this->CI->input->is_ajax_request() === FALSE  ) {            if ( ( $this->_controllers[ $controller ] === TRUE || ( is_array( $this->_controllers[ $controller ] ) && array_key_exists( $method, $this->_controllers[ $controller ] ) && $this->_controllers[ $controller ][ $method ] === TRUE ) ) ) {                show_404();            }        }    }}/*Examples * $_controllers = [ *      'my_controller_name' => TRUE //all methods must be ajax *      'my_controller_name  => [ *          'method_name' => TRUE //only the selected methods must be ajax *      ] * ] */

And configure your application/config/hooks.php file

$hook['post_controller_constructor'] = array(    'class' => 'Ajax_only',    'function' => 'eval_request',    'filename' => 'Ajax_only.php',    'filepath' => 'hooks');