The logging module of Object Cache Pro allows you to log and analyze anything your WordPress object cache does, as well as easily debug issues.

By default, Object Cache Pro uses the ErrorLogLogger which logs all critical errors to stderr using PHP’s error_log() function.

When WP_DEBUG or SAVEQUERIES is enabled, the ArrayLogger is used, which stores all log entries on a per-request basis.

You can, of course, use your own logging implementation, any PSR-3 compatible logger, or one of the included loggers such as the NullLogger.



It does nothing to keep the memory footprint low.


Stores all log entries in runtime memory and can be read using ArrayLogger::messages().

Additionally extends the ErrorLogLogger class, which logs critical errors to strerr.


All critical errors are logged to stderr using PHP error_log() function.

You can adjust the log_levels configuration option to adjust which messages are logged.

define('WP_REDIS_CONFIG', [
    'logger' => \RedisCachePro\Loggers\ErrorLogLogger::class,

    // log all messages
    'log_levels' => null,

    // only log warnings and notices
    'log_levels' => ['warning', 'notice'],


For quick debugging, the BacktraceLogger will ignore the log_levels configuration option and send all message to stderr using PHP error_log() function.

define('WP_REDIS_CONFIG', [
    'logger' => \RedisCachePro\Loggers\BacktraceLogger::class,
    'save_commands' => true,

Debug logging

Sometimes you may want to quickly debug something without creating your own logger class and just pass a function name as the logger configuration option.

define('WP_REDIS_CONFIG', [
    'logger' => 'my_debug_logger',
    'log_levels' => null, // log all messages

function my_debug_logger($level, $message, array $context = [])
    error_log("objectcache.{$level}: {$message}");

Custom Loggers

Loggers must implement the RedisCachePro\Loggers\LoggerInterface which is identical to PSR-3’s Psr\Log\LoggerInterface.

To register a logger, pass its fully qualified class name to your config:

require_once __DIR__ . '/path/to/SyslogLogger.php'

define('WP_REDIS_CONFIG', [
    'logger' => SyslogLogger::class,

An instance of it will be created when WordPress calls wp_cache_init().

To keep things simple when writing your own logger, you can extend RedisCachePro\Loggers\Logger class, which implements all necessary methods except the log() method itself:


require_once __DIR__ . '/wp-content/plugins/object-cache-pro/bootstrap.php';

class SyslogLogger extends RedisCachePro\Loggers\Logger
     * Logs with an arbitrary level to the system log.
     * @param  mixed  $level
     * @param  string  $message
     * @param  array  $context
     * @return void
    public function log($level, $message, array $context = [])
        if (! openlog('wordpress.redis', LOG_PID, LOG_USER)) {
            throw new \LogicException("Can’t open syslog for ident LOG_PID and facility LOG_USER.");

        $priority = str_replace(
            ['emergency', 'alert', 'critical', 'error', 'warning', 'notice', 'info', 'debug'],

        syslog($level, (string) $message);