active record class in codeigniter (Update)

<?php
/************* Updating Data ************************/
//Generates an update string and runs the query based on the data 
// One can pass an array or an object to the function


$data = array(
               'title' => $title,
               'name' => $name,
               'date' => $date
            );


$this -> db -> where('id', $id);
$this -> db -> update('tablename', $data); 


// By Using an object:


class Myclass {
        var $title = 'My Title';
        var $content = 'My Content';
        var $date = 'My Date';
    }


$object = new Myclass;


$this -> db -> where('id', $id);
$this -> db -> update('mytable', $object); 


// The use of the $this->db->where() function, enabling you to set the WHERE clause. 
// One can optionally pass this information directly into the update function as a string:
$this -> db -> update('tablename', $data, "id = 4");


// Using an array:
$this -> db -> update('tablename', $data, array('id' => $id));




// One may also use the $this->db->set() function described above when performing updates.
$this -> db -> update_batch();


// Generates an update string based on the data you supply, and runs the query. 
//You can either pass an array or an object to the function
$data = array(
   array(
      'title' => 'My title' ,
      'name' => 'My Name 2' ,
      'date' => 'My date 2'
   ),
   array(
      'title' => 'Another title' ,
      'name' => 'Another Name 2' ,
      'date' => 'Another date 2'
   )
);


$this -> db -> update_batch('mytable', $data, 'title'); 


//The first parameter will contain the table name, 
//the second is an associative array of values, 
//the third parameter is the where key.