Working with Redis Pub/Sub from PHP

Use a dedicated Redis subscriber connection for transient events and a separate publisher.

The objective is to understand the behavior and operational limits, not only the method name.

What It Does

Use a dedicated Redis subscriber connection for transient events and a separate publisher.

Prerequisites

Use a dedicated development environment and sample data. Where a snippet uses an injected connection, repository, request value or mailer, supply it from your own application setup.

Example 1: Basic Use

A focused working pattern for this topic. Names such as $pdo, $authContext and $repo represent dependencies provided by the application unless initialized in the snippet.

<?php
$subscriber = new Redis();
$subscriber->connect(getenv('REDIS_HOST') ?: '127.0.0.1');
$subscriber->subscribe(['events'], function (Redis $redis, string $channel, string $message): void {
    error_log($channel . ': received event');
});

Example 2: A Second Scenario

A second use case that adds a different operation or data flow specific to this topic.

<?php
$publisher = new Redis(); $publisher->connect(getenv('REDIS_HOST') ?: '127.0.0.1');
$listenerCount = $publisher->publish('events', json_encode(['kind' => 'updated'], JSON_THROW_ON_ERROR));
echo 'Listeners: ' . $listenerCount;

Example 3: Practical Checks

A practical validation, failure or deployment concern specific to this topic.

<?php
$receiver = new Redis(); $receiver->connect(getenv('REDIS_HOST') ?: '127.0.0.1');
$receiver->subscribe(['alerts'], static function (Redis $client, string $channel, string $message): void {
    if ($message === 'stop') $client->unsubscribe();
});

Important Behavior and Edge Cases

Pub/Sub has no delivery history and consumers can miss messages while disconnected.

For production use, also account for error handling, data validation, resource limits and environment-specific driver behavior.

Comparison with Related Approaches

Common Beginner Mistakes

Key Takeaways

• Use a dedicated Redis subscriber connection for transient events and a separate publisher.
• Pub/Sub has no delivery history and consumers can miss messages while disconnected.
• Use this workflow as a focused starting point rather than a substitute for application-level tests.

Choose this API or pattern when its exact semantics match your task, and verify the result against the database driver and runtime used by your application.