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

Atomically adds one to an integer key.

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

What It Does

Atomically adds one to an integer key.

Syntax and Return Value

Redis::incr(...)

The return value and exceptional cases depend on the call described here: Do not increment a noninteger string; use atomic INCR for request counters rather than get/set pairs.

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:incr:1',3);
echo $redis->incr('guide:incr: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:incr:2',4);
echo $redis->incr('guide:incr: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:incr:3',5);
echo $redis->incr('guide:incr:3');

Important Behavior and Edge Cases

Do not increment a noninteger string; use atomic INCR for request counters rather than get/set pairs.

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 adds one to an integer key.
• Do not increment a noninteger string; use atomic INCR for request counters rather than get/set pairs.
• decr atomically subtracts one.

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.