Derick Rethans has posted a new article in his series highlighting some of the changes in the latest release of Xdebug (v2.3). In this new post he talks about some of the improvements in the trace file functionality.
Trace files are a way to document every function call, and if you enable it, variable assignment and function's return values - including when these functions were called, and how much memory PHP was using at the moment of function entry (and exit). Xdebug 2.3 adds a new type of parameter rendering for stack traces and function traces through the xdebug.collect_params setting.
This new setting allows much more information to be reported back in the trace results, adding on a serialized version of the value of variables. He also shows the output results (human-readable) that shows the memory usage and time index for the execution. He also shows the new handling to include return values in the trace output using the "xdebug.trace_format" handling.