Getting query error in OOP php - php

Question

I'm just new using OOP php and I'm having a hard time to figure out how to query in database using class method. Here's my code and I've got an error which I dont know how to solve.
I declared the connection variable but I don't know why it's undefined
Notice: Undefined variable: connection
Fatal error: Call to a member function query() on a non-object in
db.php
class DbConnector {
private $serverName;
private $userName;
private $password;
private $dbName;
private $connection;
public function __construct(){
$this->serverName = "localhost";
$this->userName = "root";
$this->password = "attl";
$this->dbName = "oop";
$this->connection = new mysqli($this->serverName, $this->userName, $this->password, $this->dbName);
if ($this->connection->connect_error) {
$this->connection = die("Connection failed: " . $this->connection->connect_error);
}
}
public function getConnection(){
return $this->connection;
}
}
index.php
include('../queries/db.php');
class Users{
private $connection;
public function __construct(){
$con = new DbConnector();
$connection = $con->getConnection();
}
public function getUsers(){
$sql = $connection->query("SELECT * FROM login");
while($getUsers = $sql->fetch_array()){
echo $getUsers['username'];
}
}
}
$user = new Users();
return $user->getUsers();

Answer 1

Your problem is you're trying to access a locally scoped variable rather than a class property
public function getUsers(){
$sql = $connection->query("SELECT * FROM login"); // HERE
while($getUsers = $sql->fetch_array()){
echo $getUsers['username'];
}
}
this can't find a variable called $connection in that scope, you need to access the object property using $this.
class Users {
private $connection;
public function __construct()
{
$con = new DbConnector();
// Assign this to object propety declared above
$this->connection = $con->getConnection();
}
public function getUsers()
{
// now access the object property set in constructor.
$sql = $this->connection->query("SELECT * FROM login");
while($getUsers = $sql->fetch_array()){
echo $getUsers['username'];
}
}
}

Answer 2

Since you're declaring the following as private:
private $connection;
and including it in your construct:
public function __construct(){
$con = new DbConnector();
$connection = $con->getConnection();
You need to use $this for its property:
$this->connection = $con->getConnection();
Then changing:
$sql = $connection->query
to
$sql = $this->connection->query
in order to use the connection property.
Now, I have to admit that I am not an OOP expert and there may be another way to have solved this, yet this is what I took from it, which worked for me.