/system/classes/Kohana/Log/Writer.php

<?php defined('SYSPATH') OR die('No direct script access.');
/**
 * Log writer abstract class. All [Log] writers must extend this class.
 *
 * @package    Kohana
 * @category   Logging
 * @author     Kohana Team
 * @copyright  (c) 2008-2012 Kohana Team
 * @license    http://kohanaframework.org/license
 */
abstract class Kohana_Log_Writer {

	/**
	 * @var  string  timestamp format for log entries.
	 * 
	 * Defaults to Date::$timestamp_format
	 */
	public static $timestamp;

	/**
	 * @var  string  timezone for log entries
	 * 
	 * Defaults to Date::$timezone, which defaults to date_default_timezone_get()
	 */
	public static $timezone;

	/**
	 * Numeric log level to string lookup table.
	 * @var array 
	 */
	protected $_log_levels = array(
		LOG_EMERG   => 'EMERGENCY',
		LOG_ALERT   => 'ALERT',
		LOG_CRIT    => 'CRITICAL',
		LOG_ERR     => 'ERROR',
		LOG_WARNING => 'WARNING',
		LOG_NOTICE  => 'NOTICE',
		LOG_INFO    => 'INFO',
		LOG_DEBUG   => 'DEBUG',
	);

	/**
	 * @var  int  Level to use for stack traces
	 */
	public static $strace_level = LOG_DEBUG;

	/**
	 * Write an array of messages.
	 *
	 *     $writer->write($messages);
	 *
	 * @param   array   $messages
	 * @return  void
	 */
	abstract public function write(array $messages);

	/**
	 * Allows the writer to have a unique key when stored.
	 *
	 *     echo $writer;
	 *
	 * @return  string
	 */
	final public function __toString()
	{
		return spl_object_hash($this);
	}

	/**
	 * Formats a log entry.
	 * 
	 * @param   array   $message
	 * @param   string  $format
	 * @return  string
	 */
	public function format_message(array $message, $format = "time --- level: body in file:line")
	{
		$message['time'] = Date::formatted_time('@'.$message['time'], Log_Writer::$timestamp, Log_Writer::$timezone, TRUE);
		$message['level'] = $this->_log_levels[$message['level']];

		$string = strtr($format, $message);

		if (isset($message['additional']['exception']))
		{
			// Re-use as much as possible, just resetting the body to the trace
			$message['body'] = $message['additional']['exception']->getTraceAsString();
			$message['level'] = $this->_log_levels[Log_Writer::$strace_level];

			$string .= PHP_EOL.strtr($format, $message);
		}

		return $string;
	}

} // End Kohana_Log_Writer