我正在学习PHP，我被困在下面的代码:
<?php
class dogtag {
protected $Words;
}
class dog {
protected $Name;
protected $DogTag;
protected function bark() {
print "Woof!'n";
}
}
class poodle extends dog {
public function bark() {
print "Yip!'n";
}
}
$poppy = new poodle;
$poppy->Name = "Poppy";
$poppy->DogTag = new dogtag;
$poppy->DogTag->Words = "My name is
Poppy. If you find me, please call 555-1234";
var_dump($poppy);
?>
这是我得到的:
PHP Fatal error: Uncaught Error: Cannot access protected property poodle::$Name
这看起来很奇怪，因为我应该从子类访问受保护的变量和函数。
谁能解释一下我错在哪里?
许多谢谢。确实可以从子类访问受保护的变量。但是，你不能从子类内部访问变量。
如果将变量设置为public，则可以从类外部访问它们。
文档:http://php.net/manual/en/language.oop5.visibility.php
的例子:
Class Dog {
private $privateProperty = "private"; //I can only be access from inside the Dog class
protected $protectedProperty = "protected"; //I can be accessed from inside the dog class and all child classes
public $publicProperty = "public"; //I can be accessed from everywhere.
}
Class Poodle extends Dog {
public function getProtectedProperty(){
return $this->protectedProperty; //This is ok because it's inside the Poodle (child class);
}
}
$poodle = new Poodle;
echo $poodle->publicProperty; //This is ok because it's public
echo $poodle->getProtectedProperty(); //This is ok because it calls a public method.
你不能访问属性" Words "，你需要把它设为public
您可以添加magic方法到您的类-这将允许您从类外部访问和操作私有属性。
class foo{
private $bah;
public function __construct(){
$this->bah='hello world';
}
public function __get( $name ){
return $this->$name;
}
public function __set( $name,$value ){
$this->$name=$value;
}
public function __isset( $name ){
return isset( $this->$name );
}
public function __unset( $name ){
unset( $this->$name );
}
}
$foo=new foo;
echo $foo->bah;
$foo->bah='banana';
echo $foo->bah;