good practice in building a CRUD

Question

connectionBanco.class.php

class conexaoBanco{
    private $host="asd";
    private $login="a131";
    private $senha="123123";
    private $banco="asdasdasd";
    private $conn;

    public function dbConexao(){
        $this->conn = new PDO(
            'mysql:host='.$this->host.'; dbname=' .$this->banco.";charset=utf8", $this->login, $this->senha);
        $this->conn->exec("SET NAMES 'utf8';");
        return $this->conn;
    }

}

CRUD.class.php

include_once("conexaoBanco.class.php");

class CRUD {

    private $db;
    private $tabela = null;
    public function __construct(){
        $this->db = new conexaoBanco();
        $this->db = $this->db->dbConexao();
    }

    public function showAll($tabela,$where){
        $query = "SELECT * FROM $tabela WHERE $where";
        $sth = $this->db->prepare($query);
        $sth->execute();
        return $sth;
    }
}

running:

$sth = $sth->showAll($tabela, "status=0 GROUP BY perfil ASC");

best practices for building a better CRUD?