php-在子类中访问父类数组

Question

class Settings {
    public $constants = [
        'database' => [
            'APP_DB_HOST'       =>  'localhost'
        ],
    ];
}
class Constants extends Settings {
    public $database = [
        'APP_DB_HOST'       =>  $settings->constants['database']['APP_DB_HOST'], // not working
    ];
}

I need to access parent class array values in child class. but this $settings->constants['database']['APP_DB_HOST'] is not working for some reason.

Answer 1

Here is the working solution

<?php

class Settings {
    public $constants = [
        'database' => [
            'APP_DB_HOST'       =>  'localhost'
        ],
    ];
}
class Constants extends Settings {
    public $database;
    public function __construct(){
        $database = [
            'APP_DB_HOST'       =>  $this->constants['database']['APP_DB_HOST'], // working
        ];
    }
}

print_r(new Constants());

outputs:

Constants Object
(
    [database] => 
    [constants] => Array
        (
            [database] => Array
                (
                    [APP_DB_HOST] => localhost
                )

        )

)

as per your comment, if you want to do it in other class function, you can do that as well.

class Constants extends Settings {
    public $database;
    public function useParentHost(){
        $this->database = [
        'APP_DB_HOST'       =>  $this->constants['database']['APP_DB_HOST'], // working
    ];
    return $this->database;
    }
}

and then

$test = new Constants();
print_r($test->useParentHost());

you have to declare some function to use $this , without/outside the function this will cause an error.

Answer 2

The variable $settings does not exist, perhaps you mean $this?

$this->constants['database']['APP_DB_HOST'];

Enjoy.