README

A lightweight, flexible PSR-3 compliant logging library with configurable backends, PSR-20 Clock support, and minimal dependencies.

Drishti (दृष्टि) - Sanskrit for "Vision" or "Sight", representing the ability to see and record what happens in your application.

Features

• ✅ PSR-3 Compliant - Full implementation of the PSR-3 LoggerInterface specification
• ✅ PSR-20 Clock Support - Uses PSR-20 ClockInterface for time operations (testable and flexible)
• ✅ Minimal Dependencies - Only requires PSR-3 interface (psr/log) and PSR-20 Clock (psr/clock)
• ✅ Configurable Backends - Contract-based backend system for flexible log destinations
• ✅ Multiple Backends - Send logs to multiple destinations simultaneously
• ✅ First-Party Backends - Built-in support for stdout, stderr, files, and daily rotating files
• ✅ First-Party Formatters - Built-in SimpleLogEntryFormatter and JsonLogEntryFormatter
• ✅ Message Interpolation - Automatic placeholder replacement with context data
• ✅ Exception Handling - Automatic exception information in log entries
• ✅ All Log Levels - Supports all 8 PSR-3 log levels
• ✅ Modern PHP - Built for PHP 8.2+ with modern language features
• ✅ 100% Test Coverage - Fully tested with comprehensive test suite

Installation

Install via Composer:

composer require vaibhavpandeyvpz/drishti

Quick Start

<?php

use Drishti\Logger;

// Create a new logger instance
$logger = new Logger();

// Log messages at different levels
$logger->info('User logged in');
$logger->warning('Disk space is running low');
$logger->error('Failed to connect to database');

// Use context for message interpolation
$logger->info('User {username} logged in from {ip}', [
    'username' => 'john',
    'ip' => '192.168.1.1',
]);

// For structured logging (JSON format)
use Drishti\JsonLogEntryFormatter;
$jsonLogger = new Logger(new FileBackend('/var/log/app.json', new JsonLogEntryFormatter()));
$jsonLogger->info('User {username} logged in from {ip}', [
    'username' => 'john',
    'ip' => '192.168.1.1',
]);

// Log exceptions
try {
    // Some code that might throw
} catch (\Exception $e) {
    $logger->error('An error occurred', [
        'exception' => $e,
    ]);
}

Usage

Basic Logging

The Logger class implements the PSR-3 LoggerInterface and provides methods for all standard log levels:

use Drishti\Logger;

$logger = new Logger();

// Emergency: System is unusable
$logger->emergency('System is down');

// Alert: Action must be taken immediately
$logger->alert('Database connection lost');

// Critical: Critical conditions
$logger->critical('Application component unavailable');

// Error: Runtime errors
$logger->error('Failed to process request');

// Warning: Exceptional occurrences
$logger->warning('Deprecated API used');

// Notice: Normal but significant events
$logger->notice('User profile updated');

// Info: Interesting events
$logger->info('User logged in');

// Debug: Detailed debug information
$logger->debug('Processing request with ID: 12345');

Message Interpolation

Drishti supports PSR-3 message interpolation using placeholders in the form {key}:

$logger->info('User {username} performed {action} on {resource}', [
    'username' => 'admin',
    'action' => 'delete',
    'resource' => 'file.txt',
]);
// Output: User admin performed delete on file.txt

Context Data Types

The logger handles various context data types:

// Strings and numbers
$logger->info('Processed {count} items', ['count' => 42]);

// Booleans
$logger->info('Feature enabled: {enabled}', ['enabled' => true]);

// Arrays (JSON encoded)
$logger->info('User roles: {roles}', ['roles' => ['admin', 'user']]);

// Objects (class name or __toString() result)
$logger->info('Object: {obj}', ['obj' => $myObject]);

// Null values
$logger->info('User: {user}', ['user' => null]);

Exception Logging

When an exception is included in the context with the key exception, Drishti automatically appends exception details:

try {
    // Some code that might throw
    throw new \RuntimeException('Something went wrong', 500);
} catch (\Exception $e) {
    $logger->error('An error occurred', [
        'exception' => $e,
    ]);
}
// Output includes: [Exception: Something went wrong in /path/to/file.php:123]

Using the log() Method

You can also use the generic log() method with any valid PSR-3 log level:

use Psr\Log\LogLevel;

$logger->log(LogLevel::INFO, 'Custom log message');
$logger->log(LogLevel::ERROR, 'Error occurred', ['error_code' => 500]);

Stringable Messages

Messages can be strings or objects implementing \Stringable:

$message = new class implements \Stringable {
    public function __toString(): string
    {
        return 'Dynamic message';
    }
};

$logger->info($message);

Backend System

Drishti uses a contract-based backend system that allows you to configure where logs are written. You can use one or more backends simultaneously.

Default Behavior

If no backends are configured, Drishti uses default behavior:

• Error levels (emergency, alert, critical, error): Written to STDERR
• Informational levels (warning, notice, info, debug): Written to STDOUT

Using Backends

Configure backends when creating the logger:

use Drishti\Logger;
use Drishti\StdioBackend;
use Drishti\FileBackend;
use Drishti\DailyFileBackend;

// Single backend
$logger = new Logger(StdioBackend::stdout());

// Multiple backends
$logger = new Logger([
    StdioBackend::stdout(),
    new FileBackend('/var/log/app.log'),
]);

// Or add backends after creation
$logger = new Logger();
$logger->addBackend(StdioBackend::stdout())
       ->addBackend(new FileBackend('/var/log/app.log'));

Available Backends

StdioBackend

Writes logs to standard I/O streams (STDOUT or STDERR). Use static factory methods to create instances:

use Drishti\Logger;
use Drishti\StdioBackend;

// Write to STDOUT (ideal for containerized applications)
$logger = new Logger(StdioBackend::stdout());
$logger->info('This goes to STDOUT');

// Write to STDERR (useful for separating logs from application output)
$logger = new Logger(StdioBackend::stderr());
$logger->error('This goes to STDERR');

// With custom formatter
use Drishti\JsonLogEntryFormatter;
$formatter = new JsonLogEntryFormatter();
$logger = new Logger(StdioBackend::stdout($formatter));

// With custom clock (for testing or timezone control)
use Psr\Clock\ClockInterface;
use Samay\FrozenClock;
$clock = new FrozenClock(new \DateTimeImmutable('2024-01-15 10:00:00'));
$formatter = new JsonLogEntryFormatter($clock);
$logger = new Logger(StdioBackend::stdout($formatter));

FileBackend

Writes logs to a single file. The directory will be created automatically if it doesn't exist:

use Drishti\Logger;
use Drishti\FileBackend;

$logger = new Logger(new FileBackend('/var/log/app.log'));
$logger->info('This is written to the file');

// With custom clock
use Psr\Clock\ClockInterface;
$clock = new MyCustomClock();
$logger = new Logger(new FileBackend('/var/log/app.log', null, $clock));

DailyFileBackend

Writes logs to daily rotating files (logrotate style). Files are named with the date suffix:

use Drishti\Logger;
use Drishti\DailyFileBackend;

$logger = new Logger(new DailyFileBackend('/var/log/app'));
// Creates files like: /var/log/app-2024-01-15.log
// Automatically rotates to new file each day
$logger->info('This goes to today\'s log file');

// With custom clock (useful for testing date rotation)
use Psr\Clock\ClockInterface;
$clock = new MyCustomClock();
$logger = new Logger(new DailyFileBackend('/var/log/app', null, $clock));

Custom Backends

Create your own backend by implementing BackendInterface:

use Drishti\BackendInterface;
use Drishti\LogEntryFormatterInterface;

class DatabaseBackend implements BackendInterface
{
    public function __construct(
        private readonly \PDO $database,
        private readonly ?LogEntryFormatterInterface $formatter = null
    ) {}

    public function write(string $level, string $message, array $context): void
    {
        // Format the message using formatter (or your own logic)
        $formatted = $this->formatter?->format($level, $message, $context)
            ?? "[$level] $message";

        // Write to database, external service, etc.
        $this->database->prepare('INSERT INTO logs (level, message, context, created_at) VALUES (?, ?, ?, ?)')
            ->execute([
                $level,
                $message,
                json_encode($context),
                (new \DateTimeImmutable)->format('Y-m-d H:i:s'),
            ]);
    }
}

$logger = new Logger(new DatabaseBackend($pdo));

Multiple Backends

Send logs to multiple destinations simultaneously:

use Drishti\Logger;
use Drishti\StdioBackend;
use Drishti\FileBackend;
use Drishti\DailyFileBackend;

$logger = new Logger([
    StdioBackend::stdout(),                  // Console output
    new FileBackend('/var/log/app.log'),      // Single file
    new DailyFileBackend('/var/log/daily'),   // Daily rotating files
]);

$logger->info('This message goes to all three backends');

Formatters

Drishti includes two first-party formatters and supports custom formatters.

SimpleLogEntryFormatter (Default)

The default formatter produces human-readable log entries:

use Drishti\Logger;
use Drishti\FileBackend;
use Drishti\SimpleLogEntryFormatter;

// SimpleLogEntryFormatter is used by default
$logger = new Logger(new FileBackend('/var/log/app.log'));

// Or explicitly specify it
$formatter = new SimpleLogEntryFormatter();
$logger = new Logger(new FileBackend('/var/log/app.log', $formatter));

Output format: [2024-01-15 10:30:45] INFO: User logged in

JsonLogEntryFormatter

For structured logging, use the JSON formatter:

use Drishti\Logger;
use Drishti\FileBackend;
use Drishti\JsonLogEntryFormatter;

$formatter = new JsonLogEntryFormatter();
$logger = new Logger(new FileBackend('/var/log/app.json', $formatter));
$logger->info('User {username} logged in', ['username' => 'john', 'ip' => '192.168.1.1']);

Output format:

{
    "timestamp": "2024-01-15T10:30:45+00:00",
    "level": "INFO",
    "message": "User john logged in",
    "context": { "username": "john", "ip": "192.168.1.1" }
}

The JSON formatter includes:

• ISO 8601 timestamp
• Uppercased log level
• Interpolated message
• Exception details (if present)
• Remaining context data

Custom Formatters

You can create custom formatters by implementing LogEntryFormatterInterface:

use Drishti\LogEntryFormatterInterface;
use Psr\Clock\ClockInterface;

class CustomFormatter implements LogEntryFormatterInterface
{
    public function __construct(
        private readonly ?ClockInterface $clock = null
    ) {
        $this->clock = $clock ?? new class implements ClockInterface {
            public function now(): \DateTimeImmutable {
                return new \DateTimeImmutable;
            }
        };
    }

    public function format(string $level, string $message, array $context): string
    {
        // Your custom formatting logic
        // Interpolate message, handle exceptions, format output
        return $formatted;
    }
}

// Use custom formatter with any backend
$formatter = new CustomFormatter();
$logger = new Logger(new FileBackend('/var/log/app.log', $formatter));

PSR-20 Clock Support

Drishti uses PSR-20 ClockInterface for all time operations, making it testable and flexible. All backends and formatters accept an optional ClockInterface instance.

For testing, you can use a frozen clock like samay:

use Drishti\Logger;
use Drishti\FileBackend;
use Samay\FrozenClock;

// In tests, use a frozen clock for predictable timestamps
$fixedTime = new \DateTimeImmutable('2024-01-15 10:30:45');
$clock = new FrozenClock($fixedTime);
$logger = new Logger(new FileBackend('/var/log/test.log', null, $clock));

$logger->info('Test message');
// Timestamp will always be 2024-01-15 10:30:45

Output Format

All log entries include a timestamp in the format [YYYY-MM-DD HH:MM:SS].

Example output:

[2024-01-15 10:30:45] INFO: User john logged in from 192.168.1.1
[2024-01-15 10:30:46] ERROR: Database connection failed [Exception: Connection timeout in /app/Database.php:42]

Requirements

• PHP 8.2 or higher
• PSR-3 interface (psr/log)
• PSR-20 Clock interface (psr/clock)

For testing, we recommend samay for frozen clocks:

composer require --dev vaibhavpandeyvpz/samay

License

This project is licensed under the MIT License. See the LICENSE file for details.

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

Support

For issues, questions, or contributions, please visit the GitHub repository.