When semi-random bugs attack

When semi-random bugs attack

I have been working on a large Flex project for a while now which has been a ton of fun. The core of the application is built in Flex with a class to manage remote calling to PHP files. This is basically how the data comes and goes through the application.

While testing and developing it locally I continuously ran small tests to ensure all the data was working properly and everything was. I decide to upload a build to my online environment for the client to check out and all of a sudden the Remoting classes were returning the same error:

Client.Error.DeliveryInDoubt
Message: Channel disconnected
Detail: Channel disconnected before an acknowledgement was received

This is usually caused by a syntax error in the PHP, but it worked locally.

Charles to the rescue (again)
I opened up Charles and started looking at the response from PHP, to which I found the following:

Fatal error: Uncaught exception 'VerboseException' with message 'file_exists(): open_basedir restriction in effect. File(/models/Debug.php) is not within the allowed path(s): (/tmp)' in /PATH_REMOVED/amfphp/core/amf/io/AMFBaseDeserializer.php:380

That is saying the file can’t be loaded from the root of the server.. well obviously, but the question is, why is AMFPHP looking for it there at all?

After talking to some friends and looking around the AMFPHP files I came across a function within the “globals.php” file.

setClassMappingsPath();

This allows you to set the path, which I did, but for some reason it was still failing. After some more time spent troubleshooting I found the function definition which can be found in “amfphp/core/amf/app/Gateway.php”.

function setClassMappingsPath($value) {
$path = realpath($value . '/') . '/';
$GLOBALS['amfphp']['customMappingsPath'] = $path;
};

The realpath() function seems to be the culprit. I am not saying this is an AMFPHP error, it could be a configuration error on this web server, which I will investigate further once the project is complete.

All I did to fix the error was comment out the realpath() check and set $path = $value. That stopped the incorrect loading of the class files and “magically” my Flex application started working properly once again.

When Errors are Good
The errors in this case were not all that helpful at first, but after looking into the code they really did paint a picture. The “Delivery in doubt” error that Flex throws will prove to be your best friend if you wind up with syntax or file errors within PHP.