qcachegrind error: Unknown file format. File generated from php xdebug

I am attempting to use xdebug to profile an application written in php7.

I've written a script that sets the follow ini settings:

ini_set('xdebug.trace_format',1); // Note: I tried 0 and 2 here as well
ini_set('xdebug.profiler_enable',1);
xdebug_start_trace('/tmp/cachegrind.out');
// RUN CODE HERE
xdebug_stop_trace();

Running the script created the cachegrind files as I would expect:

root@host:/# ls /tmp | grep cachegrind
cachegrind.out.0028fd.xt
cachegrind.out.0072ab.xt
cachegrind.out.009b09.xt
cachegrind.out.025ac3.xt

Here is the first few lines of a cachegrind file so that the format is visible:

Version: 2.4.1
File format: 4
TRACE START [2016-10-28 05:26:57]
2   3784    1   0.242945    2692856
2   3785    0   0.242955    2692800 DI\Container->set   1       /path/public/api/index.php   100
2   3785    1   0.242966    2692800
2   3786    0   0.242973    2692800 spl_autoload_call   0       /path/public/api/index.php   103
3   3787    0   0.242982    2692896 Fuel\Core\Autoloader::load  1       /path/public/api/index.php   103
4   3788    0   0.242990    2692896 strpos  0       /path/fuel/core/classes/autoloader.php   219

However, when I try to open this file in qcachegrind, it fails to open:

The error message reads: "Error loading /path/to/cachegrind/file: Unknown file format

Anyone know what's going on here? I'd like to be able to use a tool like this to profile my application.

I also shelled out $30 to try opening the file in MCG but that app crashes immediately upon opening any of these files.

As a side note, the file is fairly large, but not so large that I'd expect apps to be freaking out:

❯ ls -al /Users/johnpc/repos/cachegrind.out.094ffa.xt
-rw-r--r--  1 johnpc  staff  62744095 Oct 28 02:13 /Users/johnpc/repos/cachegrind.out.094ffa.xt

that file is a trace file not a callgrind file.

i seems you set trace_output_name and profiler_output_name in the ini to the same string or trying to open the wrong file. you need to set the profiling_* variables in the ini. see: "Profiling PHP Scripts" in the xdebug docs

a sample profiling output looks like this:

    version: 1
    creator: xdebug 2.1.1rc1
    cmd: /Users/foo/bar/test1.php
    part: 1
    positions: line

    events: Time

    fl=php:internal
    fn=php::microtime

when you get problems because of the file size, you could also try the app from profilingviewer.com