如何从PHP类中到达“全局变量”

$globalVar = "Global Variable";

class MyClass {
    public function accessGlobalVar() {
        global $globalVar;
        echo $globalVar;
    }
}

$obj = new MyClass();
$obj->accessGlobalVar(); // 输出：Global Variable

$globalVar = "Global Variable";

class MyClass {
    public function accessGlobalVar() {
        echo $GLOBALS['globalVar'];
    }
}

$obj = new MyClass();
$obj->accessGlobalVar(); // 输出：Global Variable

$globalVar = "Global Variable";

class MyClass {
    private $globalVar;

    public function __construct($globalVar) {
        $this->globalVar = $globalVar;
    }

    public function accessGlobalVar() {
        echo $this->globalVar;
    }
}

$obj = new MyClass($globalVar);
$obj->accessGlobalVar(); // 输出：Global Variable