Delete from database ONLY if the uid from the database matches the uid in session

Perfect solution, was planning to answer the same while reading post on homepage ^^

You just made a little mistake :

PHP Code:

$this->session->set_userdate('uid', $userid); 


Should be :

PHP Code:

$this->session->set_userdata('uid', $userid); 


And it's more secure (to me) to make a check before accessing a session var :

PHP Code:

if($this->session->userdata('uid') === false) {
    // Throw error
} else {
    $this->db->where('pid', $pid)
             ->where('uid', $this->session->userdata('uid'))
             ->delete('dayone_entries');
}