PHP OOP insert, select from DB

<?php

class Test extends Dbn {
    
    //without prepared statements 
    public function getUsers() {
        $sql = "SELECT * FROM users";
        $stmt = $this->connect()->query($sql);
        while($row = $stmt->fetch()) {
            echo $row['firstname'];
        }
    }

    //with prepared statements 
    public function getUsersStmt($firstname, $lastname) {
        $sql = "SELECT * FROM users WHERE firstname = ? && lastname = ?";
        $stmt = $this->connect()->prepare($sql);
        $stmt->execute([$firstname, $lastname]);
        $names = $stmt->fetchAll();

        foreach ($names AS $name) {
            echo $name['firstname'] . " " . $name['lastname'];
        }
    }

    //Insert prepared statements 
    public function inserUser($firstname, $lastname, $email) {
        $sql = "INSERT INTO users (firstname, lastname, email) values (?,?,?)";
        $stmt = $this->connect()->prepare($sql);
        $stmt->execute([$firstname, $lastname, $email]);
        
    }
    
}