PHP OOP : Accessing parent attributes from child / Child inheriting from parent's attributes

Question

so the code is : DAO class

    abstract class DAO  
    {   
    protected $db; 
    protected $SQL_host='localhost';
    protected $SQL_port='3306';
    protected $SQL_dbname='projet'; 
    protected $SQL_login='root'; 
    protected $SQL_password='';

    protected function __construct()
    {
        $this->setDb(new PDO('mysql:host='.$this->SQL_host.';port='.$this->SQL_port.';dbname='.$this->SQL_dbname, $this->SQL_login, $this->SQL_password)) ;
    }

    protected function setDb(PDO $bdd)
    {
        $this->db = $bdd ;
    }


    }

and child UserDAO class

     class UserDAO extends DAO 
     {
     public function __construct()
     {
         parent::__construct();
     }
     }

When UserDAO child class inherits from parent DAO, does the child get parent's attributes ? If not, how can I make so ?

I've been looking around and they mostly tell to use get function but that's really not what i'm trying to do. Thanks for your help

Please read the PHP docs... they are a good read....

Naftali
– Naftali

2013-11-05 18:43:16 +00:00
Commented Nov 5, 2013 at 18:43 — Naftali
– Naftali, Commented Nov 5, 2013 at 18:43
Did you try to call a parent property and see what happens?

Damien Pirsy
– Damien Pirsy

2013-11-05 18:44:37 +00:00
Commented Nov 5, 2013 at 18:44 — Damien Pirsy
– Damien Pirsy, Commented Nov 5, 2013 at 18:44

Madbreaks · Accepted Answer · 2013-11-05 18:46:02Z

2

Yes, the subclass inherits the parent class's members.

answered Nov 5, 2013 at 18:46

Madbreaks

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2 Comments

adaba Over a year ago

do I have to rewrite them ? something like on the child class : protected $db = parent::db, because on my child class i'll have to use something like $request = $this->db->prepare(insert request here);

Madbreaks Over a year ago

no. your child class inherits protected $db. You can do $this->db-> ... in your child class as if it were declared in the child class itself, so long as you properly initialize it.

Joao · Accepted Answer · 2013-11-05 18:49:33Z

I had the same issue as yourself. I wanted child classes to inherit the database pdo instance. The problem was, if I had multiple models ("users" and "documents" for example), it ended up creating multiple pdo instances (super wasteful). I resorted to dependency injection. I created the instance outside the class, then passed it to any class that needed pdo:

class UserDAO extends DAO 
{
     public function __construct($db=NULL)
     {
         if($db){//if database is requested
        parent::__construct($db);
    }
     }
}

There are loads of arguments for or against dependency injection - but I found this to work the most efficiently for myself.

In answer to your question, it seems you're doing it right (though, like I said, with PDO it might not be the best). Make sure both classes are included in your script.

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