Hi there! I've been working on a fork of piwik (2.x) and I notice that when you enable the debug option, the database profiler it start to work and searching the origin of this I found in core/Tracker/Response.php this:

class Response
{
    private $timer;

    private $content;

    public function init(Tracker $tracker)
    {
        ob_start(); // we use ob_start only because of Common::printDebug, we should actually not really use ob_start

        if ($tracker->isDebugModeEnabled()) {
            $this->timer = new Timer();

            TrackerDb::enableProfiling();
        }
    }
...

The problem is that the function isDebugModeEnabled() search for a global where it depends on the debug value in the config.php.ini and it should be validated by the setting enable_sql_profiler (as I mention in the title)

My propose is this:

    public function init(Tracker $tracker)
    {
        // remove ob_start();
        if ((bool) TrackerConfig::getConfigValue('enable_sql_profiler')) {
            $this->timer = new Timer();

            TrackerDb::enableProfiling();
        }
    }

Also notice that ob_start(); cause some problems with the printDebug function (specifically with the CLI), it is completely necessary? I think this could be removed also.

I forgot to say that I search in both branch version (2.x-dev and 3.x-dev) and this is untouched between those version changes.