src/Logger/Formatter.php
public function format($event)
	{
		$output = $this->format;

		if (array_key_exists('extra', $event) === true)
		{
			$this->formatExtra($event, $event['extra']);
			$event['message'] = 'Missing Key:';
		}
		else
		{
			$event['extra'] = [];
		}

		foreach ($event as $name => $value)
		{
			if (is_array($value) === true && count($value) === 0)
			{
				$value = '';
			}
			else
			{
				$value = $this->normalize($value);
			}

			$output = str_replace('%' . $name . '%', $value, $output);
		}

		return trim($output);
	}
public function format($event)
	{
		$output = $this->format;

		if (array_key_exists('extra', $event) === true)
		{
			$this->formatExtra($event, $event['extra']);
			$event['message'] = 'Missing Key:';
		}
		else
		{
			$event['extra'] = [];
		}

		foreach ($event as $name => $value)
		{
			if (is_array($value) === true && count($value) === 0)
			{
				$value = '';
			}
			else
			{
				$value = $this->normalize($value);
			}

			$output = str_replace('%' . $name . '%', $value, $output);
		}

		return trim($output);
	}
Formats data into a single line to be written by the writer.

@param array $event event data
@return string formatted line to write to the log