PSR-3 Logger Interface compatibility

PSR-3 Logger Interface is a standards recommendation defining a common interface for logging libraries. The zend-log component predates it, and has minor incompatibilities, but starting with version 2.6 provides the following compatibility features:

PsrLoggerAdapter

Zend\Log\PsrLoggerAdapter wraps Zend\Log\LoggerInterface, allowing it to be used anywhere Psr\Log\LoggerInterface is expected.

$zendLogLogger = new Zend\Log\Logger;

$psrLogger = new Zend\Log\PsrLoggerAdapter($zendLogLogger);
$psrLogger->log(Psr\Log\LogLevel::INFO, 'We have a PSR-compatible logger');

PSR-3 log writer

Zend\Log\Writer\Psr allows log messages and extras to be forwared to any PSR-3 compatible logger. As with any log writer, this has the added benefit that your filters can be used to limit forwarded messages.

The writer needs a Psr\Logger\LoggerInterface instance to be useful, and falls back to Psr\Log\NullLogger if none is provided. There are three ways to provide the PSR logger instance to the log writer:

// Via constructor parameter:
$writer = new Zend\Log\Writer\Psr($psrLogger);

// Via option:
$writer = new Zend\Log\Writer\Psr(['logger' => $psrLogger]);

// Via setter injection:
$writer = new Zend\Log\Writer\Psr();
$writer->setLogger($psrLogger);

PSR-3 placeholder processor

Zend\Log\Processor\PsrPlaceholder adds support for PSR-3 message placeholders. Placeholder names correspond to keys in the "extra" array passed when logging a message.

Values can be of arbitrary type, including all scalars, and objects implementing __toString; objects not capable of string serialization will result in the fully-qualified class name being substituted.

$logger = new Zend\Log\Logger;
$logger->addProcessor(new Zend\Log\Processor\PsrPlaceholder);

$logger->info('User with email {email} registered', ['email' => 'user@example.org']);
// logs message 'User with email user@example.org registered'