Atomic Counters in PHP

In PHP, we don’t have built-in atomic operations like Go does. However, we can simulate similar behavior using PHP’s multi-threading extension (pthreads) and mutex locks. Here’s an example that demonstrates a similar concept:

<?php

class Counter extends Threaded {
    private $count = 0;

    public function increment() {
        $this->synchronized(function() {
            $this->count++;
        });
    }

    public function getCount() {
        return $this->count;
    }
}

class Worker extends Thread {
    private $counter;
    private $iterations;

    public function __construct(Counter $counter, $iterations) {
        $this->counter = $counter;
        $this->iterations = $iterations;
    }

    public function run() {
        for ($i = 0; $i < $this->iterations; $i++) {
            $this->counter->increment();
        }
    }
}

$counter = new Counter();
$workers = [];
$numWorkers = 50;
$iterationsPerWorker = 1000;

for ($i = 0; $i < $numWorkers; $i++) {
    $workers[] = new Worker($counter, $iterationsPerWorker);
}

foreach ($workers as $worker) {
    $worker->start();
}

foreach ($workers as $worker) {
    $worker->join();
}

echo "Final count: " . $counter->getCount() . "\n";

Let’s break down this example:

1. We define a Counter class that extends Threaded. This class has a count property and methods to increment it and get its value. The increment method uses the synchronized function to ensure thread-safe access to the count.

2. We create a Worker class that extends Thread. Each worker will increment the counter a specified number of times.

3. In the main part of the script, we create a single Counter instance and 50 Worker instances.

4. We start all the workers and then wait for them to finish using the join method.

5. Finally, we print the total count.

To run this script, you need to have the pthreads extension installed and enabled in your PHP environment. You would save this script as atomic_counter.php and run it with:

$ php atomic_counter.php
Final count: 50000

We expect to get exactly 50,000 operations. If we hadn’t used the synchronized method in our Counter class, we might get a different number, changing between runs, because the threads would interfere with each other.

Note that while this example demonstrates a similar concept to atomic counters, it’s not truly atomic in the same way as Go’s atomic operations. PHP’s threading model and synchronization primitives are different from Go’s, and this example uses mutex locks rather than atomic operations.

Also, be aware that the pthreads extension is not always available or practical to use in many PHP environments, especially in web servers. In such cases, you might need to consider alternative approaches for managing concurrent access to shared resources.