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

Atomically subtracts one from an integer-valued key.

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

What It Does

Atomically subtracts one from an integer-valued key.

Syntax and Return Value

Redis::decr(...)

The return value and exceptional cases depend on the call described here: An absent key starts from zero; noninteger values cause Redis errors.

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->set('guide:decr:1',3);
echo $redis->decr('guide:decr:1');

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);
$redis->set('guide:decr:2',4);
echo $redis->decr('guide:decr:2');

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);
$redis->set('guide:decr:3',5);
echo $redis->decr('guide:decr:3');

Important Behavior and Edge Cases

An absent key starts from zero; noninteger values cause Redis errors.

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

• Atomically subtracts one from an integer-valued key.
• An absent key starts from zero; noninteger values cause Redis errors.
• incr atomically increments a counter.

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.