请各位帮我看看我的 private $isHungry=true;为什么不提示呢？不是应该访问不到么？

<?php

header("Content-type: text/html; charset=utf-8");

date_default_timezone_set("PRC");

class Human

{

    public $name;

public $weight;

//受保护的类成员，只有自身和其子类可以访问到

protected $height;

//也是受保护的成员，只能被自身访问

    private $isHungry=true;

public function eat($food)

{

echo $this->name."'s eating ".$food."<br>";

}

}

class NbaPlayer extends Human

{

public $team='';

public $PlayNum='';

//受保护的类成员，只能别自身访问到,当public function getAge()自身定义了这个方法时，就可以被自身访问到

private $age='50';

function __construct($name,$height,$weight,$team,$PlayNum)

{

echo"construct方法被调用<br>";

   $this->name=$name;

   $this->height=$height;

$this->weight=$weight;

$this->team=$team;

   $this->PlayNum=$PlayNum;

echo $this->isHungry."\n";

}

function __destruct()

{ echo"destruct方法被调用.$this->name.<br>";

}

   //定义方法[跟原来定义函数是一样的]

public function run()

{

echo'Running<br>';

}

public function jump()

{

echo'Jumping<br>';

}

//受保护的类成员age可以被自身调用

public function getAge()

{

echo $this->name."'is age is ".($this->age)."\n";

}

}

$wang=new NbaPlayer("wang","160cm","50kg","Bull","56");

//echo $wang->getAge()."\n";

//echo $wang->height;//提示不能访问

?>