Registers a blocking callback for one or more Pub/Sub channels.
The objective is to understand the behavior and operational limits, not only the method name.
What It Does
Registers a blocking callback for one or more Pub/Sub channels.
Syntax and Return Value
Redis::subscribe(...)The return value and exceptional cases depend on the call described here: The subscriber occupies the connection until unsubscribed; use a dedicated worker or connection.
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);
$redis->subscribe(["guide.events"], static function (Redis $client,string $channel,string $message): void { echo $channel . ":" . $message . PHP_EOL; $client->unsubscribe(); });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. This additional check distinguishes the method's result from connection or statement state.
<?php
$redis = new Redis();
$redis->connect(getenv('REDIS_HOST') ?: '127.0.0.1', (int) (getenv('REDIS_PORT') ?: 6379), 2.0);
$redis->subscribe(["guide.events"], static function (Redis $client,string $channel,string $message): void { echo $channel . ":" . $message . PHP_EOL; $client->unsubscribe(); });
echo "Subscription ended after unsubscribe callback";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. This additional check distinguishes the method's result from connection or statement state.
<?php
$redis = new Redis();
$redis->connect(getenv('REDIS_HOST') ?: '127.0.0.1', (int) (getenv('REDIS_PORT') ?: 6379), 2.0);
$redis->subscribe(["guide.events"], static function (Redis $client,string $channel,string $message): void { echo $channel . ":" . $message . PHP_EOL; $client->unsubscribe(); });
echo "Dedicated Pub/Sub connection required";Important Behavior and Edge Cases
The subscriber occupies the connection until unsubscribed; use a dedicated worker or connection.
For production use, also account for error handling, data validation, resource limits and environment-specific driver behavior.
Comparison with Related Approaches
| Approach | Important distinction |
|---|---|
| Redis::subscribe | Registers a blocking callback for one or more Pub/Sub channels. |
| Related API / pattern | publish sends transient messages and reports subscriber count. |
Common Beginner Mistakes
| Mistake | Correct approach |
|---|---|
| Assuming the happy path covers edge cases | The subscriber occupies the connection until unsubscribed; use a dedicated worker or connection. |
| Using a related API interchangeably | publish sends transient messages and reports subscriber count. |
Key Takeaways
- Registers a blocking callback for one or more Pub/Sub channels.
- The subscriber occupies the connection until unsubscribed; use a dedicated worker or connection.
- publish sends transient messages and reports subscriber count.
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.