inheriting properties in php

Question

I have a superclass which contains properties & methods for setting them

class Super{
    private $property;

    function __construct($set){
        $this->property = $set;
    }
}

then I have a subclass that needs to use that property

class Sub extends Super{
    private $sub_property

    function __construct(){
        parent::__construct();
        $this->sub_property = $this->property;
    }
}

but I keep getting an error

Notice: Undefined property: Sub::$property in sub.php on line 7

where am I going wrong?

*(tip)* Since this is your second question about basic OOP features in PHP today, I suggest to have a look at the chapter [Classes and Objects in the PHP Manual](http://de2.php.net/manual/en/language.oop5.php). — Gordon, Jan 21 '11 at 16:32

score 8 · Accepted Answer · answered Jan 21 '11 at 16:23

8

The error is saying that it's trying to find a local variable called $property which doesn't exist.

To refer to $property in object context, as you intended, you need $this and the arrow.

$this->sub_property = $this->property;

secondly, the line above will fail as is because $property is private to the Super class. Make it protected instead, so it's inherited.

protected $property;

Third, (thanks Merijn, I missed this), Sub needs to extend Super.

class Sub extends Super

answered Jan 21 '11 at 16:23

Tesserex

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It is very confusing if you edit your question like that. In future, please just accept the answer or edit your question but **add** new code that shows your solution. – Gregory Jun 14 '17 at 11:31

score 3 · Answer 2 · answered Jan 21 '11 at 16:23

3

You need to make your $sub_property protected instead of private.

answered Jan 21 '11 at 16:23

jb1785

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score 2 · Answer 3 · answered Jan 21 '11 at 16:24

2

You'll also need to specify that the subclass extends from the superclass:

class Sub extends Super {
   // code
}

answered Jan 21 '11 at 16:24

mrbellek

2,300
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my bad, it is already like that in the code, have edited question to reflect this – Mild Fuzz Jan 21 '11 at 16:26

inheriting properties in php

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