PHP pthreads : impossible to create object correctly in constructor

Question

I am new to threads in PHP and I have a problem with classes extending Thread. I need to store an object given in the constructor parameters into a SplObjectStorage but I am unable to do it. The SplObjectStorage object remains empty even after attaching an object.

When I remove the "extends Thread", it works correctly but I need to use threads.

Here is an example :

<?php

class MyClass extends Thread
{
    protected $variable;
    public function __constructor($object)
    {
        $this->variable = new \SplObjectStorage;
        $this->variable->attach($object);

        $storage = new \SplObjectStorage;
        $storage->attach($object);

        var_dump($this->variable); // shows empty SplObjectStorage
        var_dump($storage); // shows SplObjectStorage with $object inside it
        var_dump($object); // shows the object
    }
    public function run() {}
}

Have you got an idea ? I want $this->variable to be like $storage after the attachment.

Thank you.

Community · Accepted Answer · 2017-05-23 10:28:02Z

The author of PHP pthreads has already answered this a couple of times on Stack Overflow.

Objects not extending Threaded aren't considered thread-safe and are therefore serialized/copied by pthreads.

You can make "thread-safe" classes from normal classes at runtime with Threaded::extend(). But be very careful. The underlying implementation might not be thread-safe. (SplObjectStorage fails here, by the way.)

I'm afraid you have to create/use SplObjectStorage thread-locally.

protected static $variable; // will be NULL in thread's context

OK, I must correct myself here a bit. I'm still in the process of learning pthreads myself.

Actually, you can use normal objects as class properties. But you have to access them somewhat unconventionally (and it's not very fast):

$storage = new \SplObjectStorage;
$storage->attach($object);
$this->variable = $storage; // object gets serialized

$storage = $this->variable // object gets unserialized

// work with $storage normally...

// ...and write it back:
$this->variable = $storage

Also note that you're working on copies when using the technique above. Other threads won't see changes until you write the object back. You might want to use Threaded::synchronized() here.

You always have to keep in mind that objects and arrays will be serialized when setting a Threaded property and unserialized when getting that property.

PS: Working with strings as Threaded properties is also very slow...

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