Profiler¶
Xdebug's own profiler. It writes into files this app reads. No account and no extra extension.
The modes¶
| Mode | What it does |
|---|---|
| Step debugging | Connects to your IDE on every request. |
| Profiling | Waits for a trigger, then writes that request's profile to a file. |
| Trace | Writes every function entry and exit. |
One or the other. Leaving two on breaks one of them, so the card makes you pick.
How to record¶
Nothing is recorded until a request asks for it. Add ?XDEBUG_TRIGGER=1 to the address you want to look at, or set the same name as a cookie. The card shows the exact trigger to use.
Controls¶
| Control | What it does |
|---|---|
| Mode | Applies one of the three modes above. |
| The recording list | The profile files that have been written. Clicking one opens its flame graph. |
| Delete | Clears the recordings. |
| Apply to container | Recreates the container when the running one disagrees with the selected mode. |
What a trace costs¶
A trace is far heavier than a profile. A single request can run to hundreds of megabytes. Record one page, then set the mode back.
The flame graph cannot draw the whole of a very long trace. When that happens the card says that what you are seeing is only the start of the request.
Worth knowing¶
- Xdebug has to be on first. Profiling is a mode of the same extension.
- A mode change does not take effect until the container is recreated. The card says when they disagree.
Coverage¶
The fourth mode, and the only one that records nothing of its own: it switches on the API PHPUnit calls, and PHPUnit writes the report. Run your tests with a coverage flag once it is applied — nothing will ever appear in the recorded list for it, and the pane says so rather than leaving you waiting.
Without it, --coverage-html produces an empty report and a warning most people never read.
Readable dumps and stack traces¶
Xdebug's develop is not a fifth mode. xdebug.mode is a list, and develop rides alongside whichever mode is chosen — so XDEBUG_MODE becomes debug,develop rather than replacing your choice. It makes var_dump readable and puts a stack trace on a warning.
It is off until asked for, because it changes what your own code prints, and a debugging tool that alters the output of the code being debugged should be something you chose.
The switch and the mode buttons are two controls over one file: moving one leaves the other exactly as it was.