Profiler

PHP code profiling allows you to inspect how much time and how many calls were made to every single function in the code.

Quickly Setup PHP for Profiling

Ensure, you have PHP installed.
Ensure Xdebug PHP extension is installed as well.
Make sure PHP zlib extension is enabled (recommended).

Check your php.ini setting:

xdebug.output_dir="<an output directory>"

Use the following launch.json setting:

{
    "name": "Launch Built-in server & Profile",
    "type": "php",
    "request": "launch",
    "runtimeArgs": [
        "-S", "localhost:8888", "-t", "."
    ],
    "noDebug": true, // <-- disable debugging
    "profile": true, // <-- enable profiling
    "openProfile": false, // <-- whether to open profiling results after session ends
}

After launching the built-in server using the launch configuration above, do a request to the web application. A new profile file (cachegrind.out.*.gz) will be created.

Opening Profiling Result

Open the file containing your profiling data. By default, it is in form of cachegrind.out.*.gz.

Using Command Palette

Bring the Command Palette, and run Open Profile File (Xdebug Profiling Output).
Choose the file, and confirm.

Drag & Drop 'cachegrind.out.*.gz' File

Alternatively, if your profile file name is in form of cachegrind.out.*.gz, you can open the file right in the Visual Studio Code editor - using File/Open File menu.

Be aware, large files may take some time to open.

Inspecting Call Times

The following view lists all the functions with the number of calls (Calls), time spent by the function body (Self Time), and time including nested calls (Time).

Inspecting Callers/Callees

The Function Details view is focused on a single function; and displays all the calling functions and all the called functions, including the time information.

Highlighting Hot Paths