我有一个（抽象的）父类，应该在构建过程中提供功能。子类可以覆盖构造函数中使用的属性：
class Parent extends MiddlewareTest
{
// abstract channel properties
protected $title = NULL;
protected $type = NULL;
protected $resolution = NULL;
function __construct() {
parent::__construct();
$this->uuid = $this->createChannel($this->title, $this->type, $this->resolution);
}
}
class Child extends Parent
{
// channel properties
protected $title = 'Power';
protected $type = 'power';
protected $resolution = 1000;
}
问题是，当未被重写的Child::__construct()运行时（使用NULL参数调用$this->createChannel），不使用重写的属性。
这在PHP中可能吗？还是每次都必须重写子构造函数才能提供所需的功能？
注意：我在php中看到了子类和父类之间共享的Properties，但这是不同的，因为子属性不是在构造函数中分配的，而是根据定义分配的。
更新
原来我的测试用例有问题。由于MiddlewareTest是基于SimpleTest单元测试用例的，所以SimpleTest实际上——我没有意识到——通过它的自动运行实例化了Parent类本身，这是从未打算过的。通过将Parent类设为抽象类修复了此问题。
经验教训：建立一个干净的测试用例，并在请求帮助之前实际运行它。
我不确定您的服务器上是如何发生这种情况的。我不得不对MiddlewareTest类进行假设，修改类名，并添加一些简单的调试行，但使用以下代码：
<?php
/**
* I'm not sure what you have in this class.
* Perhaps the problem lies here on your side.
* Is this constructor doing something to nullify those properties?
* Are those properties also defined in this class?
*/
abstract class MiddlewareTest {
// I assume this properties are also defined here
protected $title = NULL;
protected $type = NULL;
protected $resolution = NULL;
protected $uuid = NULL;
public function __construct()
{}
protected function createChannel($title, $type, $resolution)
{
echo "<pre>" . __LINE__ . ": "; var_export(array($this->title, $this->type, $this->resolution)); echo "</pre>";
echo "<pre>" . __LINE__ . ": "; var_export(array($title, $type, $resolution)); echo "</pre>";
return var_export(array($title, $type, $resolution), true);
}
}
// 'parent' is a keyword, so let's just use A and B
class A extends MiddlewareTest
{
// abstract channel properties
protected $title = NULL;
protected $type = NULL;
protected $resolution = NULL;
function __construct() {
parent::__construct();
echo "<pre>" . __LINE__ . ": "; var_export(array($this->title, $this->type, $this->resolution)); echo "</pre>";
$this->uuid = $this->createChannel($this->title, $this->type, $this->resolution);
echo "<pre>" . __LINE__ . ": "; var_export($this->uuid); echo "</pre>";
}
}
class B extends A
{
// channel properties
protected $title = "Power";
protected $type = "power";
protected $resolution = 1000;
}
$B = new B();
?>
我得到以下结果：
37: array (
0 => 'Power',
1 => 'power',
2 => 1000,
)
20: array (
0 => 'Power',
1 => 'power',
2 => 1000,
)
21: array (
0 => 'Power',
1 => 'power',
2 => 1000,
)
39: 'array (
0 => ''Power'',
1 => ''power'',
2 => 1000,
)'
正如您所看到的，正如预期的那样，这些值在实例化类中定义时被传递进来。
你能提供一些关于你的MiddlewareTest类的细节吗？这些细节可能会让你明白为什么会经历这种行为？
您运行的php版本是什么？