RedisSessionHandler.php

<?php

namespace Detain\SessionSamurai;

use Redis;
use SessionHandlerInterface;
use SessionIdInterface;
use SessionUpdateTimestampHandlerInterface;
use InvalidArgumentException;
use RuntimeException;

/**
 * Class RedisSessionHandler
 *
 * A session handler that stores PHP session data in Redis.
 */
class RedisSessionHandler implements SessionHandlerInterface, SessionIdInterface, SessionUpdateTimestampHandlerInterface
{
    /** @var Redis */
    private Redis $redis;

    /** @var int Session ttl in seconds */
    private int $ttl;

    /** @var string Prefix for all session keys in Redis */
    private string $keyPrefix;

    /**
     * @param Redis  $redis     An existing Redis connection.
     * @param int    $ttl       Session TTL in seconds.
     * @param string $keyPrefix Key prefix to isolate sessions.
     */
    public function __construct(Redis &$redis, int $ttl = 86400, string $keyPrefix = 'PHPREDIS_SESSION:') {
        $this->redis = &$redis;
        $this->ttl = $ttl;
        $this->keyPrefix = $keyPrefix;
    }

    /**
     * {@inheritdoc}
     */
    public function open(string $savePath, string $sessionName): bool
    {
        // Nothing to do since connection is done in constructor.
        return true;
    }

    /**
     * {@inheritdoc}
     */
    public function close(): bool
    {
        return $this->redis->close();
    }

    /**
     * {@inheritdoc}
     */
    public function read(string $sessionId): string
    {
        $data = $this->redis->get($this->keyPrefix . $sessionId);
        return is_string($data) ? $data : '';
    }

    /**
     * {@inheritdoc}
     */
    public function write(string $sessionId, string $data): bool
    {
        $key = $this->keyPrefix . $sessionId;
        // Use SETEX to write data and expiry at once
        return (bool) $this->redis->setex($key, $this->ttl, $data);
    }

    /**
     * {@inheritdoc}
     */
    public function destroy(string $sessionId): bool
    {
        $this->redis->del($this->keyPrefix . $sessionId);
        return true;
    }

    /**
     * {@inheritdoc}
     */
    public function gc(int $maxttl): int|false
    {
        // Redis handles expiry automatically via TTL; no action needed.
        return 0;
    }

    /**
     * {@inheritdoc}
     */
    // phpcs:ignore PSR1.Methods.CamelCapsMethodName.NotCamelCaps
    public function create_sid(): string
    {
        // Generate a 32‐byte random ID, hex‐encoded, for 64 chars.
        return bin2hex(random_bytes(32));
    }

    /**
     * {@inheritdoc}
     */
    public function validateId(string $sessionId): bool
    {
        // Check existence without resetting TTL
        return $this->redis->exists($this->keyPrefix . $sessionId) === 1;
    }

    /**
     * {@inheritdoc}
     */
    public function updateTimestamp(string $sessionId, string $data): bool
    {
        $key = $this->keyPrefix . $sessionId;
        if (!$this->redis->exists($key)) {
            return false;
        }
        // Only update TTL, do not rewrite the payload
        return (bool) $this->redis->expire($key, $this->ttl);
    }
}