"Fatal error: Call to a member function prepare() on a non-object.."

Question

Following error occures:

Fatal error: Call to a member function prepare() on a non-object

The code:

class Guestbook {

    public $db;

    public function getEntries(){
        $result = false;
        $query = 'SELECT * FROM db ORDER BY id DESC'; 

        $stmt = $this->db->prepare($query); //error in this line (17)                               
        // ...
    }   
}       

Answer 1

You have this class:

class Guestbook {
    public $db;

You never give the $db property a value, so when you do

$this->db->prepare($query);

You're basically doing

null->prepare($query);

Give $db a value in the class constructor (or make sure it's passed into the class somehow, either way..) and you'll be fine.

The

$db = new mysqli('localhost', 'root', '', 'guestbook');

In the database connection has no relation with the $db variable in the class unless you pass it into the class or make the database-initialization happen within the class.