Check out example codes for "how to prevent application from sql injection in codeigniter". It will help you in understanding the concepts better.

Code Example 1

CodeIgniter's Active Record methods automatically escape queries for you, to prevent sql injection.

$this->db->select('*')->from('tablename')->where('var', $val1);
$this->db->get();
or

$this->db->insert('tablename', array('var1'=>$val1, 'var2'=>$val2));
If you don't want to use Active Records, you can use query bindings to prevent against injection.

$sql = 'SELECT * FROM tablename WHERE var = ?';
$this->db->query($sql, array($val1));
Or for inserting you can use the insert_string() method.

$sql = $this->db->insert_string('tablename', array('var1'=>$val1, 'var2'=>$val2));
$this->db->query($sql);
There is also the escape() method if you prefer to run your own queries.

$val1 = $this->db->escape($val1);
$this->db->query("SELECT * FROM tablename WHERE var=$val1");

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