Logger

composer require quillstack/logger

PackagistSource PHP ^8.1

A logger based on PSR-3, with no dependencies beyond it.

Somewhere to write what happened, and a way to say how much of it is worth writing. A handler decides where the entries go; there is no formatter to configure and no processor to register.

Requirements

• PHP 8.1 or newer

Installation

composer require quillstack/logger

Usage

use Quillstack\LocalStorage\LocalStorage;
use Quillstack\Logger\Handlers\StorageHandler;
use Quillstack\Logger\Logger;

$logger = new Logger(new StorageHandler('/var/log/app.log', new LocalStorage()));

$logger->info('Order {id} placed by {user}', ['id' => 42, 'user' => 'ada']);

2026-08-23T10:44:17+00:00 info: Order 42 placed by ada {"id":42,"user":"ada"}

The eight methods of PSR-3 are there — emergency(), alert(), critical(), error(), warning(), notice(), info(), debug() — and log() takes the level as an argument.

What is passed alongside goes into the message

A placeholder written {id} is replaced by what the context holds under id, which is what PSR-3 §1.2 describes and what every example of using a logger shows:

$logger->error('Payment failed for {id} after {attempts} tries', ['id' => 42, 'attempts' => 3]);
// Payment failed for 42 after 3 tries

The context is still handed to the handler, because it is the part something can read rather than someone. A placeholder nothing answers is left as it was: a message reading Order placed says less than one showing what was expected.

How much is worth writing

$logger = new Logger($handler, LogLevel::WARNING);

$logger->debug('not written');
$logger->warning('written');

Anything below the minimum is not passed on, which is how debug is turned off on a server without taking the calls out of the code. setMinimumLevel() changes it later.

A level which is not one of the eight is refused with Psr\Log\InvalidArgumentException — the one the specification names — rather than written as a level nothing can ever filter on.

Where the entries go

$logger
    ->setHandler(new StorageHandler('/var/log/app.log', new LocalStorage()))
    ->addHandler(new ConsoleHandler());

setHandler() replaces whatever was there; addHandler() puts one beside it, so a file and a terminal both get the entry.

Handler	Writes
Handlers\StorageHandler	through any storage — a file, or wherever else one is implemented
Handlers\ConsoleHandler	where a person watching can see it, coloured by level

A handler is one method, so somewhere else to write is one class:

use Quillstack\Logger\HandlerInterface;

final class SyslogHandler implements HandlerInterface
{
    public function log(mixed $level, Stringable|string $message, array $context = []): bool
    {
        return syslog($this->priority($level), (string) $message);
    }
}

In an application

The framework asks the container for Psr\Log\LoggerInterface, so pointing that at a logger is all it takes:

$app = new App(__DIR__ . '/../.env', [
    LoggerInterface::class => $logger,
]);

Anything asking for a logger then has one, and the error middleware writes to it.

Technical documentation

Class	What it is
Logger	the logger, implementing Psr\Log\LoggerInterface
Level	the eight levels and how they rank; SEVERITY, name(), reaches()
Message	puts the context into the message
HandlerInterface	log(mixed $level, Stringable|string $message, array $context = []): bool
Exceptions\UnknownLevelException	a Psr\Log\InvalidArgumentException
Exceptions\HandlerNotSetException	there is nowhere to write

Unit tests

composer test
composer test:coverage
composer stan

Docker

docker-compose up -d
docker exec -w /var/www/html -it quillstack_logger sh

License

MIT. See LICENSE.