26     protected $balance = 0;  variable in BankAccount
35         return $this->balance;
41      * @param float $balance
45     protected function setBalance($balance)  argument
47         if ($balance >= 0) {
48             $this->balance = $balance;
57      * @param float $balance
61     public function depositMoney($balance)  argument
63         $this->setBalance($this->getBalance() + $balance);
71      * @param float $balance
75     public function withdrawMoney($balance)  argument
77         $this->setBalance($this->getBalance() - $balance);