PHP OOP Update Protected String on Extended Class __construct

Question

I'm trying to create my first PHP class and have been stuck on how to update protected strings.

What i'm trying to do is create an extended class that works with protected strings from the main class.

I'm able to update the string when the first class loads, but when I load my extended class it does not show the updated text.

What am I doing wrong?

class test {
    protected $testing = 'test';

    function __construct(){
        echo "The Test class has loaded (".$this->testing.")";
        $this->testing='changed';
        echo "Updated to (".$this->testing.")";
    }
}

class test2 EXTENDS test {

    function __construct(){
        echo "The Test2 class has loaded (".$this->testing.")";
        $this->testing='updated';
        echo 'The string has been updated to ('.$this->testing.')';
    }
}

$blah = new test();
$blah2 = new test2();

The results i'm trying to get are:

The Test class has loaded (test) Updated to (changed)

The Test2 class has loaded (changed) The string has been updated to (updated)

Answer 1

You need to construct the parent. Just because a child class extends a parent class, doesn't mean that the parent class automatically is created/constructed when the child class is. It just inherits the functionality (properties / methods).

You can do this with: parent::__construct();

I made a few small edits to your source, notably PSR-2 styled class names and line breaks. But everything else is the same.

<?php

class Test {
    protected $testing = 'original';

    function __construct(){
        echo "The Test class has loaded (".$this->testing.")\n";
        $this->testing = 'Test';
        echo "Updated to (".$this->testing.")\n";
    }
}

class TestTwo extends test {

    function __construct(){
        echo "Child class TestTwo class has loaded (".$this->testing.")\n";
        parent::__construct();
        echo "Parent class Test class has loaded (".$this->testing.")\n";
        $this->testing = 'TestTwo';
        echo "The string has been updated to (".$this->testing.")\n";
    }
}

$test = new Test();
$testTwo = new TestTwo();

Which will give you the following output:

The Test class has loaded (original)
Updated to (Test)
Child class TestTwo class has loaded (original)
The Test class has loaded (original)
Updated to (Test)
Parent class Test class has loaded (Test)
The string has been updated to (TestTwo)

Answer 2

Objects don't affect class state while program continues running which means those two instantiations are apart from each other. However, you can keep the changes to the class instead using static properties:

class test
{
    protected static $testing = 'test';

    function __construct()
    {
        echo "The Test class has loaded (" . self::$testing . ")";
        self::$testing = 'changed';
        echo "Updated to (" . self::$testing . ")";
    }
}

class test2 extends test
{
    function __construct()
    {
        echo "The Test2 class has loaded (" . self::$testing . ")";
        self::$testing = 'updated';
        echo 'The string has been updated to (' . self::$testing . ')';
    }
}

$blah = new test();
echo PHP_EOL;
$blah2 = new test2();

Output:

The Test class has loaded (test)Updated to (changed)
The Test2 class has loaded (changed)The string has been updated to (updated)