PHP Redis: Get All Keys Matching Pattern (Detailed Guide w/ Code Examples)

Use Case(s)

Finding keys in a Redis database matching a certain pattern is useful when you want to perform a mass operation on these keys, or need to filter keys based on specific criteria.

Code Examples

Let's assume we have a few keys such as user:1, user:2, user:3 and we're looking for all keys starting with 'user'.

The Predis client library can be used to connect PHP with Redis:

require "vendor/autoload.php";
Predis\Autoloader::register();

$client = new Predis\Client();
$keys = $client->keys('user:*');
print_r($keys);

The keys method of the Predis client object is used to fetch all keys that match a given pattern. The '*' character is a wildcard that matches any sequence of characters.

Best Practices

• Since using KEYS command can be expensive in production as it might lead to blocking the entire Redis instance while scanning keys, consider using SCAN if possible.
• Always limit the number of keys being fetched at one time to prevent memory issues.

Common Mistakes

• Using the wrong type of wildcard can lead to unexpected results. Be sure you understand how wildcards work in Redis.
• Forgetting that key scanning in Redis is case-sensitive.

FAQs

• Q: Can I use multiple patterns in a single KEYS command? A: No, the Redis KEYS command only supports a single pattern.
• Q: What happens if there are no keys matching the pattern? A: The KEYS command returns an empty list if no keys match the pattern.