PHP Redis::publish() Method: Usage and Examples

Sends a message to subscribers of a Redis channel and returns the number of receivers.

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

What It Does

Sends a message to subscribers of a Redis channel and returns the number of receivers.

Syntax and Return Value

Redis::publish(...)

The return value and exceptional cases depend on the call described here: Pub/Sub messages are ephemeral; subscribers that are offline do not receive past events.

Requirements: install and enable the corresponding PHP driver or extension and configure the service before running the examples.

Example 1: Basic Use

Requires the phpredis extension and a running Redis server. Keys use a guide-specific prefix; clean up example keys after experimenting.

<?php
$redis = new Redis();
$redis->connect(getenv('REDIS_HOST') ?: '127.0.0.1', (int) (getenv('REDIS_PORT') ?: 6379), 2.0);
echo $redis->publish("guide.events", 'draft') . " active subscribers";

Example 2: A Second Scenario

Requires the phpredis extension and a running Redis server. Keys use a guide-specific prefix; clean up example keys after experimenting.

<?php
$redis = new Redis();
$redis->connect(getenv('REDIS_HOST') ?: '127.0.0.1', (int) (getenv('REDIS_PORT') ?: 6379), 2.0);
echo $redis->publish("guide.events", 'review') . " active subscribers";

Example 3: Practical Checks

Requires the phpredis extension and a running Redis server. Keys use a guide-specific prefix; clean up example keys after experimenting.

<?php
$redis = new Redis();
$redis->connect(getenv('REDIS_HOST') ?: '127.0.0.1', (int) (getenv('REDIS_PORT') ?: 6379), 2.0);
echo $redis->publish("guide.events", 'published') . " active subscribers";

Important Behavior and Edge Cases

Pub/Sub messages are ephemeral; subscribers that are offline do not receive past events.

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

• Sends a message to subscribers of a Redis channel and returns the number of receivers.
• Pub/Sub messages are ephemeral; subscribers that are offline do not receive past events.
• Streams provide durable event processing when retention is required.

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.