一旦创建了扩展的对象，就调用类方法

Question

Assume we have the following class (simplified):

class SuperConfig {
    public $mainDir;

    public function setDir() {
        $this->mainDir = "path/to/dir";
    }
}

This class is supposed to be extended in EVERY other class in the project, and I do need the setDir() function of the parent to be executed. Obviously, I could do it like this:

class A extends SuperConfig() {
    public function __construct() {
        parent::setDir();
    }
    // ... other stuff is about to be done ...
}

and I could access the properties in the child class like this:

class A extends SuperConfig {
    public function doSomething() {
        SuperConfig::mainDir;
    }
}

This is a viable solution, but I got multiple hundreds of classes and doing this in every single one seems tedious. So, is there a way to do something like this:

class SuperConfig {
    public $mainDir;

    public function __extend() {
        $this->setDir();
    }

    public function setDir() {
        $this->mainDir = "path/to/dir";
    }
}

__extend() obviously doesn't work like that, but I'm wondering is there is a trick how I could make this work.

Answer 1

class SuperConfig {
    public $mainDir;

    public function __construct() {
        $this->setDir();  // consider moving setDir's code here as well,
                          // unless you have a good reason for it to be a method
    }

    public function setDir() {
        $this->mainDir = "path/to/dir";
    }
}

You simply do this, and then you expect all subclasses to call the parent constructor if they're overriding the constructor:

public function __construct() {
    parent::__construct();
    // more code
}

It's perfectly reasonable to expect children to call their parent constructor, unless they deliberately want to leave the instance in an unknown and potentially broken state.