Referencing A Parent Class' Other Children

[Millar]

Hello,

 

I want class db (which extends class base) to be able to access class conf (which extends class base).

 

When I print out the information of the base (parent class) class, I can access variables/functions defined in the base, db and conf classes.

 

When I print the information of the db class (child of base) I can access variables/functions of only the base and db classes. So why can I not reference variables from my config class from within the sibling class?

 

Thanks.

 

Here is the print_r output:

conf Object
(
    [db_host] => localhost
    [db_user] => *
    [db_pass] => *
    [db_database] => *
    [db_prefix] => *
    [db_type] => *
    [version] => 1.0
)

db Object
(
    [connection] => 
    [version] => 1.0
)

base Object
(
    [version] => 1.0
    [conf] => conf Object
        (
            [db_host] => *
            [db_user] => *
            [db_pass] => *
            [db_database] => *
            [db_prefix] => *
            [db_type] => *
            [version] => 1.0
        )

    [db] => db Object
        (
            [connection] =>
            [version] => 1.0
        )

)

Why does db Object not look like this?:

db Object
(
    [connection] => 
    [version] => 1.0
    [conf] => conf Object
        (
            [db_host] => *
            [db_user] => *
            [db_pass] => *
            [db_database] => *
            [db_prefix] => *
            [db_type] => *
            [version] => 1.0
        )
)

[trq]

So why can I not reference variables from my config class from within the sibling class?

 

Because they are not related. What does base hold that needs to be shared between config and db?

[svivian]

I think I'm having a similar problem. I have a class, artist_control, which has an instance of another class, database, as a variable (for connecting to database, executing queries, etc). Also in my artist_control class, in one of the functions I have an instance of an artist class. My artist class needs to access my database class in order to run some SQL queries.

 

How can I do this? I tried using global $db; (the variable was set in artist_control) but that didn't work. Is it a good idea to pass in the $db variable (perhaps by reference)?

[svivian]

Oh, I also can't have the $db as part of my artist class instead, because there will be other classes (eg album) that will need it too.

[svivian]

Hmm... well for now I've set $db as a global variable from the artist_control class, but there must be a better way of doing it, surely?

[BrandonK]

Why can't your artist class create its own instance of the db?  Use a singleton pattern if you are afraid of multiple connections, but why should one class have to share with another?  What if your artist_control class changes completely to a different database type?

 

My thought would be to create layers, and don't make them dependent on each other.

[aschk]

If you think about it from a semantic point of view, is "artist_control" really a descendent of "database" ? It USES a database, but as far as I can make out it doesn't DESCEND (i.e isn't a child) of database.

 

Why not have your artist_control simply use a database connection.

e.g.

class artist_control {
  private $dbconn;

  public function __construct(){
    $this->dbconn = new Database();
  }

  public function getArtists(){
    $artists = $this->dbconn->query("SELECT * FROM arists");
    return $artists;
  }
}

 

Even better (as brandon mentioned) have the Database class be a singleton, meaning you can use $this->dbconn = Database::getInstance(); and share this between any other classes that require db connectivity. This saves database connections (although php will merge them for you) and memory for allocation of new classes.