Xdebug Update: August 2023

London, UK

Tuesday, September 12th 2023, 09:27 BST

In this monthly update I explain what happened with Xdebug development in the past month. These are normally published on the first Tuesday on or after the 5th of each month.

Patreon and GitHub supporters will get it earlier, around the first of each month.

You can become a patron or support me through GitHub Sponsors. I am currently 36% towards my $2,500 per month goal, which is set to allow continued maintenance of Xdebug.

If you are leading a team or company, then it is also possible to support Xdebug through a subscription.

In the last month, I spend around 27 hours on Xdebug, with 32 hours funded.

Towards Xdebug 3.3

In August I mostly spent my time on improving Xdebug’s xdebug_get_function_stack() function and stack traces with regard to chained exceptions.

A feature request asked whether it would be possible to add the local variables for each stack frame that is returned with the xdebug_get_function_stack() function. Xdebug can already show local variables for the top most frame when it shows stack traces (through the xdebug.show_local_vars setting), but the function’s result don’t include them.

When implementing this feature, I noticed that arguments were being returned as strings, instead of actual values, as part of each stack frame. I created an issue for that and implemented that as well.

When the original requester tried out the new feature, it turned out that he wanted to do this in a user-defined exception handler. However, at that stage, the original stack has been destroyed, and Xdebug no longer could access that information.

To work around this, I now cache the stack when an exception gets thrown so that the cached version then can be requested when calling xdebug_get_function_stack() with the new from_exception option.

That looks like:

<?php
class Handlers
{ function __construct(private string $title, private float $PIE) {} static function exceptionHandler($exception) { $s = xdebug_get_function_stack( [ 'from_exception' => $exception ] ); var_dump($s); }
} class Error_Entry
{ public function __construct($base, $errno) { throw new Exception(); }
} set_exception_handler(['Handlers', 'exceptionHandler']);
$e = new Error_Entry(1, 2); ?> 

Xdebug’s cache is eight items big, which allows for 8 rethrown/chained exception stacks to be remembered.

Because of this cache it was now also (finally) possible to resolve issue #450 and issue #476. This now means that chained and rethrown exceptions are now displayed when Xdebug shows a stack trace, whether it is on the CLI, or in an html context.

Over the next few months I will continue to work on the features and issues on the 3.3 roadmap, without any guarantees these tickets will be implemented.

If you have comments, suggestions, or if your company wants to help fund features, please reach out, or leave comments on the document.

Xdebug Videos

I have published one new videos in the last month:

• PHP: Debugging FFI and PHP

Let me know what you’d like to see!

You can find all previous videos on my YouTube channel.

Business Supporter Scheme and Funding

In the last few months, two new business supporters signed u