So it just took me all night to figure out that in Xdebug ‘tracing’ is different to ‘profiling’.

It didn’t help that the xdebug.trace_output_name included an example format of ‘cachegrind.out.%s’. Why would you name a trace file cachegrind.out if only profile files are in cachegrind format!?

In my efforts to get profiling to work I found myself loading trace files into KCachegrind and getting the rather unhelpful message: “Could not open the file “/run/shm/xdebug/trace…xt”. Check it exists and you have enough permissions to read it.”

So the error message is about file permissions. I checked and checked and checked again but the file permissions were OK. The problem was I was loading a trace file, not a profile file.

So I gave up on KCachegrind and tried to get webgrind to work. Turns out loading a trace file (not a profile file) into webgrind doesn’t work either. I got the same problem reported by Sven about ‘parsers is undefined’. I fucked around trying to update the jquery.tablesorter plugin in webgrind, but the problem was due to the fact I was loading a tracing file, not a profiling file.

In the end I got it all figured out. Here’s my /etc/php5/mods-enabled/xdebug.ini file:

zend_extension=/usr/lib/php5/20131226/xdebug.so
xdebug.remote_enable=1
xdebug.remote_handler=dbgp
xdebug.remote_mode=req
;xdebug.remote_host=127.0.0.1
xdebug.remote_host=10.1.1.203
;xdebug.remote_port=9000
xdebug.remote_port=9999

; http://www.xdebug.org/docs/all

xdebug.profiler_enable=1
xdebug.profiler_output_dir=/run/shm/xdebug
xdebug.profiler_output_name=cachegrind.out.%t.%R

xdebug.auto_trace=1
xdebug.collect_assignments=1
xdebug.collect_includes=1
xdebug.collect_params=4
xdebug.collect_return=1
xdebug.collect_vars=0
xdebug.show_mem_delta=1
;2 for HTML:
xdebug.trace_format=0
xdebug.trace_options=1
xdebug.trace_output_dir=/run/shm/xdebug
xdebug.trace_output_name=trace.%t.%R
xdebug.var_display_max_children=-1
xdebug.var_display_max_data=-1
xdebug.var_display_max_depth=-1

The above config supports generation of tracing files and profiling files. I can now load my profiling files into KCachegrind and webgrind.

Everything is easy when you know how!