<?php

$sentryTraceHeader = $request->getHeaderLine('sentry-trace');
$baggageHeader = $request->getHeaderLine('baggage');

$transactionContext = \Sentry\Tracing\TransactionContext::continueFromHeaders($sentryTraceHeader, $baggageHeader);

// Start the transaction
$transaction = \Sentry\startTransaction($transactionContext);

...

$transactionContext = new \Sentry\Tracing\TransactionContext();

// Start a nested transaction
// In this case, we would not continue the trace and instead start a new one.
$transaction = \Sentry\startTransaction();

https://sentry.io/organizations/sentry-sdks/performance/sentry-php:c81f843eb6474d53aca7902229cbe32a

---

$transactionContext = \Sentry\Tracing\TransactionContext::fromParent($transaction);
// Start a nested transaction
$transaction = \Sentry\startTransaction($transactionContext);

public static function fromParent(Transaction $transaction)
{
    $context = new self();
    $context->traceId = $transaction->getTraceId();
    $context->parentSpanId = $transaction->getParentSpanId();
    $context->sampled = $transaction->getSampled();
    $context->getMetadata()->setBaggage($transaction->getBaggage());

    return $context;
}

https://sentry.io/organizations/sentry-sdks/performance/sentry-php:a2e3d29c847e49ebac13ce9448254af6

// - How would someone fetch the current transaction? SentrySdk::getCurrentHub()->getTransaction()?
// - Should we auto populate this inside TransactionContext::__construct()?