如何在子 class 构造方法中获取父 class 变量值

Question

I have two files:

ParentClass.php

<?php

class ParentClass {

    public $variable1;
    public $variable2 = "Value of variable 2";

    public function __construct()
    {
        $this->variable1 = "Value of variable 1";
    }
}

$obj = new ParentClass;

?>

And ChildClass.php

<?php

include "ParentClass.php";

class ChildClass extends ParentClass {

    public function __construct()
    {
            echo $this->variable1;
            echo $this->variable2;
    }
}

$obj = new ChildClass;

?>

When I run the ChildClass file in browser, it gives me the the value of only variable 2. It does not show the value of variable1. I need to print both variable1 and variable2 values. Please Help.

Answer 1

you need to call parent::__construct() in your child contruct

the working code should be:

ParentClass.php

<?php

class ParentClass {

    public $variable1;
    public $variable2 = "Value of variable 2";

    public function __construct()
    {
        $this->variable1 = "Value of variable 1";
    }
}

$obj = new ParentClass;

?>

And ChildClass.php

<?php

include "ParentClass.php";

class ChildClass extends ParentClass {

    public function __construct()
    {
            parent::__construct(); // like this
            echo $this->variable1;
            echo $this->variable2;
    }
}

$obj = new ChildClass;

?>

TRY this and see if it works:)