chore(functions): add more logging methods (GoogleCloudPlatform#1220)

Author: Ace Nassri

functions/log_helloworld/index.php

@@ -37,9 +37,17 @@ function helloLogging(ServerRequestInterface $request): string
     // This doesn't log anything
     error_log('error_log does not log in Cloud Functions!');
 
+    // This will log an error message and immediately terminate the function execution
+    // trigger_error('fatal errors are logged!');
+    
     // For HTTP functions, this is added to the HTTP response
     // For CloudEvent functions, this does nothing
     var_dump('var_dump goes to HTTP response for HTTP functions');
+    
+    // You can also dump variables using var_export() and forward
+    // the resulting string to Cloud Logging via an fwrite() call.
+    $entry = var_export('var_export output can be captured.', true);
+    fwrite($log, $entry);
 
     // Functions must return a String or PSR-7 Response object
     return '';