<?php
class A {
    private $_con;
    public function __construct($id) {
        $this->_con = DB_ODBC::connect($id);
    }
    public function exec($stmt) {
        return odbc_execute($this->_con, $stmt);
    }
    public function B_Obj() {
        return new B(..);
    }
}
class B extends {
    // ..
}
$a = new A(2);
$b_1 = $a->B_Obj();
$b_2 = new B(..);
?>