src/Zipkin/RealSpan.php
public function annotate(string $value, ?int $timestamp = null): void
    {
        if (!isValid($timestamp)) {
            throw new InvalidArgumentException(
                sprintf('Valid timestamp represented microtime expected, got \'%s\'', $timestamp)
            );
        }

        $this->recorder->annotate($this->traceContext, $timestamp, $value);
    }
public function annotate(string $value, ?int $timestamp = null): void
    {
        if (!isValid($timestamp)) {
            throw new InvalidArgumentException(
                sprintf('Valid timestamp represented microtime expected, got \'%s\'', $timestamp)
            );
        }

        $this->recorder->annotate($this->traceContext, $timestamp, $value);
    }
Associates an event that explains latency with the current system time.

@param string $value A short tag indicating the event, like "finagle.retry"
@param int|null $timestamp
@return void
@throws \InvalidArgumentException
@see Zipkin\Annotations