Setting up Cloud Trace for PHP

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You can enable Cloud Trace for PHP applications by using OpenCensus. OpenCensus is a set of instrumentation libraries for collecting trace and metric data that work with multiple backends. For the latest details about OpenCensus for PHP, along with additional documentation and examples, go to opencensus-php-exporter-stackdriver.

Installing the library

  1. Install the OpenCensus Stackdriver exporter composer package:

    composer require opencensus/opencensus-exporter-stackdriver

    The previous command also installs the OpenCensus and Trace composer packages.

  2. To use the framework integrations described in a later section on this page, install the OpenCensus extension:

    pecl install opencensus-alpha
  3. Add the following line to your php.ini file:
  4. If you're on Windows, then download the DLL file from the pecl download page to your extension directory of your PHP installation and add the following line to your php.ini file:


Configuring the client

To enable the OpenCensus library for PHP, complete the following steps:

  1. Import the required classes:

    use OpenCensus\Trace\Exporter\StackdriverExporter;
    use OpenCensus\Trace\Tracer;
  2. Initialize the StackdriverExporter object:

    $exporter = new StackdriverExporter([
        'clientConfig' => [
            'projectId' => $projectId

    If you are running on Google Cloud infrastructure, then you don't need to set projectId to your Google Cloud project ID. If you don't set this field, the client library for PHP automatically gathers this data from a Google Cloud metadata server.

    If you aren't running on Google Cloud infrastructure, then you must supply your Google Cloud project ID to your application.

    Regardless of your infrastructure, for PHP, when you don't explicitly set the Google Cloud project ID, the google-cloud PHP library, which is invoked by OpenCensus, automatically determines if the environment variable GOOGLE_CLOUD_PROJECT is set, and if so, the library uses the value of GOOGLE_CLOUD_PROJECT as your Google Cloud project ID. For more information, see Authentication. To set the environment variable, do the following:

    Linux or macOS

    export GOOGLE_CLOUD_PROJECT=your-project-id


    set GOOGLE_CLOUD_PROJECT=your-project-id


  3. Start the tracer:


Create the exporter and start the tracer as early as possible in your application.


You can customize the behavior of the Cloud Trace library for PHP. For a list of exporter configuration options, go to opencensus-php-exporter-stackdriver or to OpenCensus PHP API.

App Engine flexible environment lets you reduce the performance impact of reporting trace data by having the data sent by a background process. To enable background reporting, do the following:

  1. Modify the runtime_config section of your app.yaml file to specify the enable_stackdriver_integration flag:

    enable_stackdriver_integration: true

    This flag causes the PHP batch processing daemon, BatchRunner, to be spawned.

  2. Set the environment variable IS_BATCH_DAEMON_RUNNING to true.

  3. Include the async option with the value set to true in the clientConfig options passed to the OpenCensus StackdriverExporter. For more details, see StackdriverExporter.

Add custom Trace span

The Cloud Trace library for PHP automatically creates a trace record for each HTTP request. You can also add custom trace spans within the request:

    ['name' => 'slow_function'],
    function () {

Framework integrations

The OpenCensus library provides useful integrations for web frameworks and functions. For more details, go to available integrations and examples for some frameworks.

Configure your platform

You can use Cloud Trace on Google Cloud and other platforms.

Running on Google Cloud

When your application is running on Google Cloud, you don't need to provide authentication credentials in the form of a service account to the client library. However, you do need to ensure that your Google Cloud platform has the Cloud Trace API access scope enabled.

For a list of supported Google Cloud environments, see Environment support.

For the following configurations, the default access-scope settings enable the Cloud Trace API:

  • App Engine flexible environment
  • App Engine standard environment

  • Google Kubernetes Engine (GKE)

  • Compute Engine

  • Cloud Run

If you use custom access scopes, then you must ensure that Cloud Trace API access scope is enabled:

  • For information about how to configure the access scopes for your environment by using the Google Cloud console, see Configuring your Google Cloud project.

  • For gcloud users, specify access scopes using the --scopes flag and include the trace.append Cloud Trace API access scope. For example, to create a GKE cluster with only the Cloud Trace API enabled, do the following:

    gcloud container clusters create example-cluster-name --scopes=

Running locally and elsewhere

If your application is running outside of Google Cloud, then you must provide authentication credentials in the form of a service account to the client library. The service account must contain the Cloud Trace agent role. For instructions, see Creating a service account.

Google Cloud client libraries use Application Default Credentials (ADC) to find your application's credentials.

You can provide these credentials in one of three ways:

  • Run gcloud auth application-default login

  • Place the service account in a default path for your operating system. The following lists the default paths for Windows and Linux:

    • Windows: %APPDATA%/gcloud/application_default_credentials.json

    • Linux: $HOME/.config/gcloud/application_default_credentials.json

  • Set the GOOGLE_APPLICATION_CREDENTIALS environment variable to the path to your service account:


    export GOOGLE_APPLICATION_CREDENTIALS=path-to-your-service-accounts-private-key


    set GOOGLE_APPLICATION_CREDENTIALS=path-to-your-service-accounts-private-key



Viewing the traces

After deployment, you can view the traces in the Google Cloud console Trace Viewer.

Go to the Trace Viewer page


For information on troubleshooting issues with Cloud Trace, go to the Troubleshooting page.