The following class definition lists three vars, yet they are all treated as one, as the call to report() shows.  I'd love to be able to define more vars in a class.

<?
class bankaccount {

     var $balance;
     var $transactions;
     var $history;

     function bankaccount () {
          $this->$balance = 0.00;
          $this->$transactions = 0;
          $this->$history[$transactions] = $this->$balance;
     }

     function report () {
          echo $this->$balance . "<br>";
          echo $this->$transactions . "<br>";
          echo $this->$history[$transactions] . "<br>";
     }

     function credit ($amount) {
          $amount = abs($amount);
          $this->$balance += $amount;
     }

     function debit ($amount) {
          $amount = abs($amount);
          $this->$balance -= $amount;
     } 

}

$USDaccount = new bankaccount;
$USDaccount->credit(10000);
$USDaccount->debit(1000);
$USDaccount->debit(.78);

$USDaccount->report();

?>

the result is:

8999.22
8999.22
8999.22

Why?