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Last Reviewed: February 14, 2025

SERVER_NAME and SERVER_PORT on Pantheon

Learn how to work around SERVER_NAME and SERVER_PORT variables in your Pantheon Website Management Platform environment configuration.

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Some code relies on $_SERVER['SERVER_NAME'] and $_SERVER['SERVER_PORT'] to construct URLs, either to "call itself" or to create URLs that are passed to third parties and expect to be routed back. This doesn't work well on Pantheon because the environmental data will be for ephemeral container data.

In general, you don't want your code to rely on this, but some extensions (themes, modules, plugins) give you no choice. In that case, you will need to modify the $_SERVER variable in your settings.php (Drupal) or wp-config.php (WordPress) file to ensure the right values are present.

Use PANTHEON_HOSTNAME Instead of SERVER_NAME

PANTHEON_HOSTNAME is added in wp-config-pantheon.php and constructed from HTTP_HOST (if available) or the Pantheon environment if HTTP_HOST is unavailable (e.g. in WP-CLI). If the $_SERVERvariable is set to 'SERVER_NAME', the URL generated for a request will be something similar to https://endpoint05ccd237.chios.panth.io instead of the intended https://yourdomain.com.

Adding the following code will pass the correct value when 'SERVER_NAME' is used:

$_SERVER['SERVER_NAME'] = PANTHEON_HOSTNAME;

PANTHEON_HOSTNAME can be overridden by defining the constant manually in your wp-config.php file before the wp-config-pantheon.php file is required as noted in the wp-config.php documentation.

While this fix does correct symptoms such as undesirable URLs, we recommended replacing all instances of 'SERVER_NAME' with 'HTTP_HOST' directly (e.g. WP_HOME and WP_SITE for WordPress).

Note

$_ENV will also be around for command-line uses. $_SERVER is only set up when handling a web initiated request.

Set SERVER_PORT Correctly

Certain applications (like SimpleSAML) require specific port values to be set at the web server level, before our GlobalCDN. Use the snippet below to assign port value 443 for nginx when the headers specify HTTPS:

if (isset($_ENV['PANTHEON_ENVIRONMENT'])) {
  if (isset($_SERVER['HTTP_USER_AGENT_HTTPS']) && $_SERVER['HTTP_USER_AGENT_HTTPS'] === 'ON') {
    $_SERVER['SERVER_PORT'] = 443;
  }
  else {
    $_SERVER['SERVER_PORT'] = 80;
  }
}

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