Helper

Each helper file is simply a collection of functions in a particular category. For example, we have a booking_list_helper.php file.

<?PHP
//file name booking_list_helper.php
function custom_helper($data){
    // start writing code here   
}
?>

Loading of booking_list_helper.php

For loading helper file go to the autoload.php under config folder of your extension add helper file in the array, use $extension_helper variable. you can add multiple helper files into this array, they will be loaded automatically by my_controller.

//file name autoload.php
$extension_helper  = array(
                      'booking_list_helper'
                     );