如何在扩展类中访问父PHP类属性

Question

I tried accessing parent class properties in its daughter class but I keep getting this error Fatal error: undefined class constant 'arms' on line 26 of blabla.php. This is my code below in blabla.php

blabla.php

<?php
class mother
{
  public $legs;
  public $arms;
  public $eyes;


   function say($arm,$eye,$leg)
  {
   $this->arms =  'pretty';
   $this->eyes = 'stunning';
   $this->legs = 'beautiful slim';
  }
  }


class daughter extends mother
{
 public $newArms;
 public $newEyes;
 public $newLegs;

 public function newSay()
 {
   $this->newArms = parent::arms;
   $this->newEyes = parent::eyes;
   $this->newLegs = parent::legsparent::arms;
   echo 'I have a beautiful daughter who has '.$this->newArms.' arms, '.$this->newEyes.' eyes and '.$this->newLegs.' legs';
 }

}


$baby = new daughter();
$baby->newSay();


?>

if there is a mistake in my code, please show me and how to correct it. Thanks in advance.

Answer 1

You got your syntax wrong.

ClassName::NAME

is used to access class constants as your errormessage says.

A class constant is defined using the const keyword in the class' body.

However, you want to access the property of an object. You have to use $this for that

Inside a methods body: $this->propertyName . You have to make sure that the property is visible to its child classes, so you either need to make it protected or public or have the magic __get method implemented or have custom getters and setters defined and call them instead of the actual property.

You also don't use the parent keyword for this. parent always looks for static fields of the parent class and is generally not tied to an instance. (You can however use it to call a method from the parent class in the context of its child class)