php - extending classes issue -

i have master class several separate classes want link can share variables defined in master class. problem first slave class can read $x variable, every subsequent slave class (i have 20 others) shows $x blank. 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 doing wrong here? i've never used extended classes before i've no idea i'm doing :)

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;     } }