PHP object inheritage from class constructor - the right way

Question

I need some guidance about an php object inheritage situation. I have: a configuration object like:

configuration{
    var driver = 'mysql'; // or 'mssql';
    var host = 'database_host';
    var user = 'database_user';
    var password = 'database_password';
    var name = 'database_name';
}

two database handler classes:

class mysql{
    public mysql(){} // connect
    public query(){} // set a query
    public result(){} // load result
}

class mssql{
    public mysql(){} // connect
    public query(){} // set a query
    public result(){} // load result
}

and some kind of class controller:

class database{
    public function __construct(){
        $configuration = new configuration;
        /*
         * now, depending on the value of the $configuration->driver
         * my database class must inherit methods from mysql or mssql class
         */
        switch( $configuration->driver ){
            case 'mysql':
                // database inherit mysql methods
            break;
            case 'mssql':
            // database inherit mssql methods
            break;
        }
    }
}

usage like:

$database = new database;
$database->query( 'select * from some_table' );
$result = $database->result();

so, when I use my database class methods, depending on configuration object, I actually use mysql or mssql methods. the way i see it is not passible because I want my database class to inherit another class in the class constructor.

I was hoping that someone could give me an advice about how can I do this.. let's say.. the right way.

Thanks.

I'm not seeing any inheritance here - is it database that should be extending something? — halfer
– halfer, Commented Feb 2, 2013 at 12:34
You seem to be talking about a 'factory' pattern. Look it up, it may assist to answer your question — thaJeztah
– thaJeztah, Commented Feb 2, 2013 at 12:34
for halfer question, I would like some kind of dinamically extend; the thing is that i dont know what is the parent class until that 'switch' in the database contructor. — stef
– stef, Commented Feb 2, 2013 at 12:46
for thaJeztah, I will document about the factory pattern, thanks — stef
– stef, Commented Feb 2, 2013 at 12:48

Community · Accepted Answer · 2017-05-23 11:48:50Z

1

nonono, this is not oop-thinking. You should google the following keywords:

When you did, put the switch statement into the factory, make the class mysql an interface named DBDriver, and use the strategy pattern in your database class.

edited May 23, 2017 at 11:48

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answered Feb 5, 2013 at 14:51

Francois Bourgeois

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1 Comment

stef Over a year ago

Thanks, i'll do some research. The thing is that, before posting this question I have read about 'interface', and I didn't quite get the use of it. I'll be back, after research :-)

stef · Accepted Answer · 2013-03-25 18:38:38Z

If someone, as confusend as me, reads this post, this is the solution I found (after weeks of research - yes, after weeks):

using singleton pattern, create a parent class called database:

class database{
    protected static $instances = array();

    // method to create a new instance of this object
    public function getInstance( $driver ){
        $instanceid = md5( $driver );

        if( self::$instances[ $instanceid ] == null ){
            self::$instances[ $instanceid ] = new $driver;
        }

        return self::$instances[ $instanceid ];
    }

    public function testFunction(){
        //do something else
    }
}

then create driver functions

class mysql extends database{
    public mysql(){} // connect
    public query(){} // set a query
    public result(){} // load result
}

class mssql extends database{
    public mysql(){} // connect
    public query(){} // set a query
    public result(){} // load result
}

now use it like

$database = database::getInstance( 'mysql' );
$database->query(); // works
$database->testFunction(); // works to

and further on you can use and like

$database = database::getInstance( 'mssql' );
$database->query(); // works
$database->testFunction(); // works to

I need to apologize to Froncoise for unchecking his answer as the right one.

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