PHP fatal error : Can't inherit abstract function

Question

我不明白我做错了什么......

abstract class Css {
    abstract protected function parse($data);
}

abstract class CssElem extends Css {
    abstract protected function parse($data);
}

class Modifier extends CssElem {
    function __construct($data = null) {
        if( $data )
            $this->parse ($data);
    }

    protected function parse($data) {
       // Some code...
    }
}

它给了我:

[Mon Jul 8 13:21:10 2013] PHP Fatal error: Can't inherit abstract function Css::parse() (previously declared abstract in CssElem) in /home/arthur/NetBeansProjects/capa/CssElem.php on line 21 [Mon Jul 8 13:21:10 2013] 127.0.0.1:41207 [500]: / - Can't inherit abstract function Css::parse() (previously declared abstract in CssElem) in /home/arthur/NetBeansProjects/capa/CssElem.php on line 21

第 21 行是 CssElem 中的抽象 protected 函数 parse($data);。

我对Java中的OOP比较熟悉，但根据the doc似乎还可以...

Answer 1

尝试将您的中级类(class)更改为:

abstract class CssElem extends Css {
    // abstract protected function parse($data); // <-- take this away
}

另请参阅this comment在文档中。

引用评论:

An abstract class that extends an abstract class can pass the buck to its child classes when it comes to implementing the abstract methods of its parent abstract class.

然而，这似乎将在下一个PHP version 7.2中被允许:

It is now allowed to override an abstract method with another abstract method in a child class. (https://wiki.php.net/rfc/allow-abstract-function-override)