src/Agent.php
public function startTransaction(string $appname, string $license = null): bool
    {
        if (!$this->isLoaded()) {
            return false;
        }

        if (isset($license)) {
            return newrelic_start_transaction($appname, $license);
        }

        return newrelic_start_transaction($appname);
    }
public function startTransaction(string $appname, string $license = null): bool
    {
        if (!$this->isLoaded()) {
            return false;
        }

        if (isset($license)) {
            return newrelic_start_transaction($appname, $license);
        }

        return newrelic_start_transaction($appname);
    }
Starts a new transaction, usually after manually ending a transaction.

Agent version 3.0.5.95 or higher.

@see https://docs.newrelic.com/docs/agents/php-agent/php-agent-api/newrelic_start_transaction
@see self::endTransaction

@param string $appname The application name to associate with data from this transaction
@param string $license (optional) Provide a different license key if you want the transaction to report
to a different New Relic account

@return bool