Problem with references in php5

Question

Let me start right off the code:

<?php
class Father{
    function Father(){
        echo 'A wild Father appears..';
    }

    function live(){
        echo 'Some Father feels alive!';
    }
}

class Child{
    private $parent;
    function Child($p){
        echo 'A child is born :)';
    }

    function setParent($p){
        $parent = $p;
    }

    function dance(){
        echo 'The child is dancing, when ';
        $parent -> live();
    }
}

$p = new Father();
$p -> live();
$c = new Child($p);
$c -> dance();

?>

When running this I get an error on Line 24 saying "PHP Fatal error: Call to a member function live() on a non-object in ../test.php on line 24" I've searched the web for a while now and can't find a solution for this to work. Can someone help me with my poor understanding of php5?

Did you know that constructors should be named __construct instead of NameOfTheClass in PHP5? — ThiefMaster
– ThiefMaster, Commented Apr 15, 2011 at 23:58
No, I didn't. I'm just learning the language since I've got to write something in it for a project. Thanks for your advice :) — Fiona Runge
– Fiona Runge, Commented Apr 16, 2011 at 0:03

ThiefMaster · Accepted Answer · 2011-04-16 07:58:04Z

3

You need to use $this->parent->live() to access the member variable. Additionally, you have to assign the parent object to it.

class Child{
    private $parent;
    function __construct($p){
        echo 'A child is born :)';
        $this->parent = $p; // you could also call setParent() here
    }

    function setParent($p){
        $this->parent = $p;
    }

    function dance(){
        echo 'The child is dancing, when ';
        $this->parent -> live();
    }
}

Besides that, you should rename your constructor methods to __construct which is the suggested name in PHP5.

edited Apr 16, 2011 at 7:58

answered Apr 15, 2011 at 23:58

ThiefMaster

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1 Comment

Fiona Runge Over a year ago

Aah! That's good to know :) - 9 Minutes to go until this may become the solution ^^

Daniel · Accepted Answer · 2011-04-16 00:00:26Z

2

You didn't call setParent in your constructor.
This will fix it:

function Child($p){
    echo 'A child is born :)';
    $this->setParent($p);
}

answered Apr 16, 2011 at 0:00

Daniel

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1 Comment

ThiefMaster Over a year ago

Usually getters/setters are for the external interface and internally accessing the field directly is better.

SIFE · Accepted Answer · 2011-04-16 01:36:51Z

0

First, the preferred method to use constructor in PHP5 by using __construct keyword. When you access to class member you should to use $this, witch in your case you didn't when you tried to parent member.

function setParent($p){
        $parent = $p;
    }

Make it like this:

function setParent($p){
        $this->parent = $p;
    }

And this:

   function dance(){
        echo 'The child is dancing, when ';
        $parent -> live();
    }

To this:

   function dance(){
        echo 'The child is dancing, when ';
        $this->parent -> live();
    }

You will be end with this:

$p = new Father();
$p -> live();
$c = new Child();
$c -> setParent($p);
$c -> dance();

You don't need pass the parent to the child constructor as you will set it in setParent method.

edited Apr 16, 2011 at 1:36

answered Apr 16, 2011 at 0:11

SIFE

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