Parent::method does not return connection

Question

I have a class Conn connecting to an SQL Server:

class Conn
{
    protected $con;
    protected $a = 'aaa';

    function __construct()
    {
        $this -> conecta();
    }

    private function conecta(){
        $serverName = "xxx.xxx.xxx.xxx";
        $connectionInfo = array( "Database"=>"XXX", "UID"=>"YYY", "PWD"=>"ZZZ", "CharacterSet" => "UTF-8");

        try {
            $conn = sqlsrv_connect($serverName, $connectionInfo);
        } catch (Exception $e) {
            echo "Erro na conexão com o BD.<br/>";
            die( print_r(sqlsrv_errors(), true));
        }

        if (!$conn){
            echo "Erro na conexão com o BD.<br/>";
            die( print_r(sqlsrv_errors(), true));
        } else {
            $this -> con = $conn;
            var_dump($this -> con);
        }
    }

    protected function getCon(){
        return $this -> con;
    }

}

And a class BD that stretches the class Conn:

class BD extends Conn
{
    private $cnx;

    function __construct()
    {
        $this -> cnx = parent::getCon();
        var_dump($this -> cnx);
    }
}

---

When I create an object of BD:

If in the method getCon() i set return $this -> a;, get back to me: string(3) "aaa"

If in the method getCon() i set return $this -> con;, get back to me: NULL where it should return resource(3) of type (SQL Server Connection)

---

I wonder what could be causing this or if I’m using it incorrectly.

Answer 1

The object $con in Conn is only initialized when the method is called Conn::conecta, which in turn is called in the builder of Conn, but the builder of Conn is never called, for the method was superscripted in the daughter class BD.

If you need to override the constructor, you will need to call the parent constructor explicitly:

class BD
{
    public function __construct()
    {
        parent::__construct();
        // ...
    }
}

Thus, the mother class constructor will be executed, calling the method conecta and initiating the object $con. This way, you can do:

class BD
{
    public function __construct()
    {
        parent::__construct();
        $this->cnx = $this->getCon();
    }
}

Note that it was invoked as $this->getCon(), since, as the method Conn::getCon is protected, it will be inherited in BD as private, being still accessible within the class.