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I am a learner of php. So i just joined with you. I need help to understand the php code. I have seen a php file. where has a line of code was $CI =& get_instance() so Please explane me the line of code. Full code of the file given bellow ------------------------------------------------------------------------------------- if (!defined('BASEPATH')) exit('No direct script access allowed');require_once(FUEL_PATH.'models/base_module_model.php');class Courses_model extends Base_module_model { public $record_class = 'Course'; public $required = array( 'title' => 'Please fill out the course name', 'slug' => 'Slug cannot be empty', ); function __construct() { $CI =& get_instance(); $this->config->module_load(COURSE_FOLDER, COURSE_FOLDER); $this->_tables = $CI->config->item('tables'); parent::__construct($this->_tables['courses']); $this->load->module_model(COURSE_FOLDER, 'lessons_model'); } function list_items($limit = NULL, $offset = NULL, $col = 'title', $order = 'asc') { $data = parent::list_items($limit, $offset, $col, $order); return $data; } function form_fields($values = array()) { $fields = parent::form_fields($values); unset($fields['created_at']); return $fields; } function get_courses($where = array(), $order_by ='title', $limit = NULL, $offset = NULL, $return_method = NULL, $assoc_key = NULL) { $courses = $this->db->get($this->_tables['courses'])->result_array(); if($courses) { foreach($courses as &$course) { $course['lessons'] = $this->db->where(array('course_id' => $course['id']))->get($this->_tables['lessons'])->result_array(); if(is_array($course['lessons'])) { foreach ($course['lessons'] as $key => &$lesson) { $lesson['articles_count'] = $this->db->where(array('lesson_id' => $lesson['id']))->get($this->_tables['articles'])->num_rows(); } } } } return $courses; }}class Course_model extends Base_module_record { private $_tables; function on_init() { $this->_tables = $this->_CI->config->item('tables'); }}