浏览器中的php出现空白但在cli中显示输出

Question

I have the following code from google adwords api and for some reason there is a specific section that prevents the browser from displaying output. I can't figure out why but can someone please tell me how to fix and why this line would prevent the browser from displaying output but allows the cli to display output.

<?php
// Include the initialization file
require_once 'src/Google/Api/Ads/AdWords/init.php';

require_once ADWORDS_UTIL_PATH . '/ReportUtils.php';


/**
 * Runs the example.
 * @param AdWordsUser $user the user to run the example with
 * @param string $filePath the path of the file to download the report to
 */
function DownloadCriteriaReportExample(AdWordsUser $user, $filePath) {
  // Load the service, so that the required classes are available.
  $user->LoadService('ReportDefinitionService', ADWORDS_VERSION);

  // Create selector.
  $selector = new Selector();
  $selector->fields = array('CampaignName', 'AdGroupName', 'Criteria',
      'AverageCpc', 'Impressions', 'Clicks', 'Cost', 'AveragePosition', 'Ctr');

  // Filter out deleted criteria.
  $selector->predicates[] = new Predicate('Status', 'NOT_IN', array('DELETED'));

  // Create report definition.
  $reportDefinition = new ReportDefinition();
  $reportDefinition->selector = $selector;
  $reportDefinition->reportName = 'Criteria performance report #' . uniqid();
  $reportDefinition->dateRangeType = 'LAST_30_DAYS';
  $reportDefinition->reportType = 'CRITERIA_PERFORMANCE_REPORT';
  $reportDefinition->downloadFormat = 'CSV';

  // Exclude criteria that haven't recieved any impressions over the date range.
  $reportDefinition->includeZeroImpressions = FALSE;

  // Set additional options.
  $options = array('version' => ADWORDS_VERSION, 'returnMoneyInMicros' => FALSE);

  // Download report.
  ReportUtils::DownloadReport($reportDefinition, $filePath, $user, $options);

  printf("Report with name '%s' was downloaded to '%s'.
",
      $reportDefinition->reportName, $filePath);
}

This is the line that is causing the issue for some reason

// Don't run the example if the file is being included.
if (__FILE__ != realpath($_SERVER['PHP_SELF'])) {

  return;
}

End of line causing issue

try {
  // Get AdWordsUser from credentials in "../auth.ini"
  // relative to the AdWordsUser.php file's directory.
  $user = new AdWordsUser();

  // Log every SOAP XML request and response.
  $user->LogAll();

  // Download the report to a file in the same directory as the example.
  $filePath = dirname(__FILE__) . '/report.csv';


  // Run the example.
  DownloadCriteriaReportExample($user, $filePath);


} catch (Exception $e) {
  printf("An error has occurred: %s
", $e->getMessage());
}