# Logging (PHP SDK)

The Market Data PHP SDK supports PSR-3 compatible logging for debugging and monitoring API interactions.

## Default Logging

The SDK creates a default logger based on the `MARKETDATA_LOGGING_LEVEL` environment variable:

```php
<?php

// Set logging level via environment variable
putenv('MARKETDATA_LOGGING_LEVEL=debug');

use MarketDataApp\Client;

$client = new Client();

// Debug messages will be logged to stderr
$quote = $client->stocks->quote('AAPL');
```

### Available Log Levels

The SDK supports standard PSR-3 log levels:

| Level       | Description                         |
|-------------|-------------------------------------|
| `emergency` | System is unusable                  |
| `alert`     | Action must be taken immediately    |
| `critical`  | Critical conditions                 |
| `error`     | Error conditions                    |
| `warning`   | Warning conditions                  |
| `notice`    | Normal but significant conditions   |
| `info`      | Informational messages              |
| `debug`     | Debug-level messages (most verbose) |

## Custom Logger

Inject your own PSR-3 compatible logger:

### Monolog

```php
<?php

use MarketDataApp\Client;
use Monolog\Logger;
use Monolog\Handler\StreamHandler;
use Monolog\Handler\RotatingFileHandler;

// Create Monolog logger
$logger = new Logger('marketdata');

// Log to file with rotation
$logger->pushHandler(new RotatingFileHandler(
    '/var/log/marketdata/api.log',
    maxFiles: 7,
    level: Logger::DEBUG
));

// Also log errors to stderr
$logger->pushHandler(new StreamHandler(
    'php://stderr',
    level: Logger::ERROR
));

// Pass logger to client
$client = new Client(logger: $logger);

$quote = $client->stocks->quote('AAPL');
```

### Custom PSR-3 Logger

```php
<?php

use MarketDataApp\Client;
use Psr\Log\AbstractLogger;
use Psr\Log\LogLevel;

// Create a simple custom logger
class SimpleLogger extends AbstractLogger
{
    public function log($level, $message, array $context = []): void
    {
        $timestamp = date('Y-m-d H:i:s');
        $contextStr = !empty($context) ? json_encode($context) : '';
        echo "[{$timestamp}] [{$level}] {$message} {$contextStr}\n";
    }
}

$logger = new SimpleLogger();
$client = new Client(logger: $logger);

$quote = $client->stocks->quote('AAPL');
```

## What Gets Logged

The SDK logs the following events:

### Debug Level
- API request URLs and parameters
- Response status codes
- Retry attempts

### Info Level
- Successful API responses
- Rate limit information

### Warning Level
- Retry attempts after transient failures
- Deprecated endpoint usage

### Error Level
- API errors and exceptions
- Authentication failures
- Network errors

## Example Log Output

```
[2024-01-15 10:30:00] [debug] Making request: GET https://api.marketdata.app/v1/stocks/quotes/?symbol=AAPL
[2024-01-15 10:30:01] [debug] Response received: 200 OK
[2024-01-15 10:30:01] [info] Rate limits - Used: 1, Remaining: 9999, Limit: 10000
```

## Disabling Logging

To disable logging, set the log level to a high threshold or provide a null logger:

```php
<?php

use MarketDataApp\Client;
use Psr\Log\NullLogger;

// Option 1: Use NullLogger
$client = new Client(logger: new NullLogger());

// Option 2: Set high log level via environment
putenv('MARKETDATA_LOGGING_LEVEL=emergency');
$client = new Client();
```

## Production Recommendations

- Use `warning` or `error` level in production to reduce log volume
- Use `debug` level only during development or troubleshooting
- Configure log rotation to prevent disk space issues
- Consider using structured logging (JSON format) for log aggregation systems