Using thread in php, ununderstood behaviour

Question

here is a simple example of what I am not understanding :

<?php

class classA {

    private $z = 1;

    public function __construct() {
        $this->b = new classB;
        $this->b->setRefonClassA($this);
        $this->b->start();
    }

    function changeZ() {
        echo "ChangeZ : z=" . $this->z . "\n";
        $this->z = 666;
        echo "ChangeZ : z=" . $this->z . "\n";
    }

    function showZ() {
        echo "showZ : z=" . $this->z . "\n";
    }

}

class classB extends Thread {

    function setRefOnClassA($classA) {
        $this->classA = $classA;
    }

    function run() {
        $this->classA->changeZ();
        $this->classA->showZ();
    }

}

$test = new classA(); ?>

The result are :

ChangeZ : z=1  
ChangeZ : z=666  
showZ : z=1

I was expecting that showZ=666. Why z=1 ?
I'm clearly missing something here.
Thanks in advance

Community · Accepted Answer · 2017-05-23 12:12:40Z

1

Can you try extending classA from Stackable?

There is a similar problem:

pthread Thread objects reset their state

edited May 23, 2017 at 12:12

CommunityBot

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answered Nov 10, 2013 at 16:52

Lajos Veres

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3 Comments

Hugo y Over a year ago

If classA extends Stackable it seems that it's not allowed to start the b thread. (Error : Warning: pthreads has detected an attempt to start classB from an invalid context, the creating context must start classB in ...)

Lajos Veres Over a year ago

Strange. The linked problem seems to be really similar.

Hugo y Over a year ago

My bad, it works if I do exactly as showed in the example you linked.

Joe Watkins · Accepted Answer · 2013-11-11 07:39:25Z

1

Read this: https://gist.github.com/krakjoe/6437782

You have two problems, first classA is not thread safe, if you don't descend from pthreads it is serialized when set as a member of classB. If classA does descend from pthreads, when you write it to classB you loose the real reference and pthreads will not allow you to access the same functionality - it thinks you are in another thread.

The key is, "You are responsible for the objects you create", this means, if you intend to share an object among threads, you must retain a direct reference to it in the scope that created the object.

answered Nov 11, 2013 at 7:39

Joe Watkins

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