php - extending classes issue

Question

I have a master class with several separate classes that I want to link up together so I can share variables defined in the master class. The problem is only the first slave class can read the $x variable, every subsequent slave class (I have 20 others) shows $x as blank. For example:

class Master {
    var $x;
    function initialize{) {
        $this->x = 'y';
    }   
}

class Slave1 extends Master {
    function process(){
        echo $this->x;
    }
}
class Slave2 extends Master {
    function process(){
        echo $this->x;
    }
}

Am I doing something wrong here? I've never used extended classes before so I've no idea what I'm doing :)

Can you show the calling code? Are you running ->initialize() on every single instance? — ircmaxell
– ircmaxell, Commented Feb 23, 2011 at 16:50
its good practice to use access modifier instead of using var — Gaurav
– Gaurav, Commented Feb 23, 2011 at 16:51
If you want process to echo 'y' you'll need to add __construct to the Master class. Or call initialize on manually — JohnP
– JohnP, Commented Feb 23, 2011 at 16:54
@SeRPRo You should not edit the question that way, you should post your solution as an answer. — Albin Sunnanbo
– Albin Sunnanbo, Commented Feb 23, 2011 at 16:56
@Albin sorry I thought he needs to approve the changes. Sorry :) — SERPRO
– SERPRO, Commented Feb 23, 2011 at 16:59

Gaurav · Accepted Answer · 2011-02-23 16:59:46Z

3

class Master {
    var  $x;  // should use protected or public
    function __construct() {
        $this->initialize();
    }

    function initialize{) {
       $this->x = 'y';
    }   
}

class Slave1 extends Master {
    function process(){
        echo $this->x;
    }
}
class Slave2 extends Master {
    function process(){
        echo $this->x;
    }
}

edited Feb 23, 2011 at 16:59

answered Feb 23, 2011 at 16:57

Gaurav

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Nick Clark · Accepted Answer · 2011-02-23 18:56:08Z

1

For completeness, here is a copy of Gaurav's answer using visibility modifiers (private, protected, public).

class Master {
    protected $x;
    public function __constructor() {
        $this->x = 'y';
    }
}

class Slave1 extends Master {
    public function process() {
        // do stuff
        echo $this->x;
    }
}

class Slave2 extends Master {
    public function process() {
        // do other stuff
        echo $this->x;
    }
}

// Usage example
$foo = new Slave1();
$bar = new Slave2();
$foo->process();
$bar->process();

answered Feb 23, 2011 at 18:56

Nick Clark

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