Using Redis as a PHP Cache Backend

Cache computed values with explicit expiration and a consistent naming scheme.

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

What It Does

Cache computed values with explicit expiration and a consistent naming scheme.

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
$key = 'cache:product:' . $productId;
$json = $redis->get($key);
if ($json === false) {
    $product = $repo->load($productId);
    $json = json_encode($product, JSON_THROW_ON_ERROR);
    $redis->setex($key, 300, $json);
}
$data = json_decode($json, true, 512, JSON_THROW_ON_ERROR);

Example 2: A Second Scenario

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

<?php
$key = 'cache:article:' . $articleId;
$redis->set($key, json_encode($article, JSON_THROW_ON_ERROR), ['ex' => 120]);
echo $redis->ttl($key);

Example 3: Practical Checks

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

<?php
try { $encoded = $redis->get('cache:settings'); }
catch (RedisException $e) { $encoded = false; error_log('Cache temporarily unavailable'); }
$settings = $encoded === false ? $database->loadSettings() : json_decode($encoded, true, 512, JSON_THROW_ON_ERROR);

Important Behavior and Edge Cases

Treat the cache as optional: misses and outages must not corrupt the source of truth.

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

• Cache computed values with explicit expiration and a consistent naming scheme.
• Treat the cache as optional: misses and outages must not corrupt the source of truth.
• 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.