如何让php中类中的所有函数都可以访问变量？

class MyClass {
    public $myVariable;

    public function myFunction() {
        // 可以在函数中直接访问 $myVariable
        echo $this->myVariable;
    }
}

class MyClass {
    private $myVariable;

    public function setMyVariable($value) {
        $this->myVariable = $value;
    }

    public function getMyVariable() {
        return $this->myVariable;
    }

    public function myFunction() {
        // 可以通过函数来访问和修改 $myVariable
        echo $this->getMyVariable();
    }
}