My Pantheon wp-config.php template.

pantheon-wp-config.php

<?php

define( 'SITE_LIVE_DOMAIN', SITE_LIVE_DOMAIN );

define( 'WP_ENV', isset( $_ENV['PANTHEON_ENVIRONMENT'] ) ? $_ENV['PANTHEON_ENVIRONMENT'] : 'local' );
define( 'SCHEME', isset( $_SERVER['HTTP_USER_AGENT_HTTPS'] ) && $_SERVER['HTTP_USER_AGENT_HTTPS'] == 'ON' ? 'https' : 'http' );

// Redirect all traffic on live site to the correct domain
if ( 'live' === WP_ENV && php_sapi_name() !== 'cli' ) {
	if ( $_SERVER['HTTP_HOST'] !== SITE_LIVE_DOMAIN ) {
		header( 'HTTP/1.0 301 Moved Permanently' );
		header( 'Location: https://' . SITE_LIVE_DOMAIN . $_SERVER['REQUEST_URI'] );
		exit();
	}
}

// Set home and site url
if ( isset( $_SERVER['HTTP_HOST'] ) ) {
	define( 'WP_HOME', SCHEME . '://' . $_SERVER['HTTP_HOST'] );
	define( 'WP_SITEURL', SCHEME . '://' . $_SERVER['HTTP_HOST'] );
}

// Pantheon Environment
if ( isset( $_ENV['PANTHEON_ENVIRONMENT'] ) ) {

	define( 'DB_NAME', $_ENV['DB_NAME'] );
	define( 'DB_USER', $_ENV['DB_USER'] );
	define( 'DB_PASSWORD', $_ENV['DB_PASSWORD'] );
	define( 'DB_HOST', $_ENV['DB_HOST'] . ':' . $_ENV['DB_PORT'] );
	
	/**#@+
	 * @link https://api.wordpress.org/secret-key/1.1/salt/
	 */
	define( 'AUTH_KEY', $_ENV['AUTH_KEY'] );
	define( 'SECURE_AUTH_KEY', $_ENV['SECURE_AUTH_KEY'] );
	define( 'LOGGED_IN_KEY', $_ENV['LOGGED_IN_KEY'] );
	define( 'NONCE_KEY', $_ENV['NONCE_KEY'] );
	define( 'AUTH_SALT', $_ENV['AUTH_SALT'] );
	define( 'SECURE_AUTH_SALT', $_ENV['SECURE_AUTH_SALT'] );
	define( 'LOGGED_IN_SALT', $_ENV['LOGGED_IN_SALT'] );
	define( 'NONCE_SALT', $_ENV['NONCE_SALT'] );
	/**#@-*/

	// Don't show deprecations; useful under PHP 5.5
	error_reporting( E_ALL ^ E_DEPRECATED );

	// Force the use of a safe temp directory when in a container
	if ( defined( 'PANTHEON_BINDING' ) ) {
		define( 'WP_TEMP_DIR', sprintf( '/srv/bindings/%s/tmp', PANTHEON_BINDING ) );
	}

	// FS writes aren't permitted in test or live, so we should let WordPress know to disable relevant UI
	if ( in_array( WP_ENV, array( 'test', 'live' ) ) && ! defined( 'DISALLOW_FILE_MODS' ) ) {
		define( 'DISALLOW_FILE_MODS', true );
	}

}

// Local Environment
if ( 'local' === WP_ENV ) {

	// Check for local config file
	if ( file_exists( dirname( __FILE__ ) . '/wp-config-local.php' ) ) {

		require_once( dirname( __FILE__ ) . '/wp-config-local.php' );

	} else {

		define( 'DB_NAME', DB_NAME );
		define( 'DB_USER', 'root' );
		define( 'DB_PASSWORD', 'root' );
		define( 'DB_HOST', 'localhost' );
		define( 'SCRIPT_DEBUG', true );

		/**#@+
		 * @link https://api.wordpress.org/secret-key/1.1/salt/
		 */
		define( 'AUTH_KEY', 'put your unique phrase here' );
		define( 'SECURE_AUTH_KEY', 'put your unique phrase here' );
		define( 'LOGGED_IN_KEY', 'put your unique phrase here' );
		define( 'NONCE_KEY', 'put your unique phrase here' );
		define( 'AUTH_SALT', 'put your unique phrase here' );
		define( 'SECURE_AUTH_SALT', 'put your unique phrase here' );
		define( 'LOGGED_IN_SALT', 'put your unique phrase here' );
		define( 'NONCE_SALT', 'put your unique phrase here' );
		/**#@-*/
	}

}

if ( ! defined( 'DB_CHARSET' ) ) {
	define( 'DB_CHARSET', 'utf8' );
}

if ( ! defined( 'DB_COLLATE' ) ) {
	define( 'DB_COLLATE', '' );
}

if ( ! defined( 'WPLANG' ) ) {
	define( 'WPLANG', '' );
}

if ( ! defined( 'IMAGE_EDIT_OVERWRITE' ) ) {
	define( 'IMAGE_EDIT_OVERWRITE', true );
}

if ( ! defined( 'WP_DEBUG' ) ) {
	define( 'WP_DEBUG', 'live' !== WP_ENV );
}

if ( ! defined( 'WP_POST_REVISIONS' ) ) {
	define( 'WP_POST_REVISIONS', 10 );
}

if ( ! defined( 'DISALLOW_FILE_EDIT' ) ) {
	define( 'DISALLOW_FILE_EDIT', true );
}

if ( ! defined( 'ABSPATH' ) ) {
	define( 'ABSPATH', dirname( __FILE__ ) . '/' );
}

if ( ! isset( $table_prefix ) ) {
	$table_prefix = 'wp_';
}

require_once( ABSPATH . 'wp-settings.php' );