The Stopwatch Component

The Stopwatch component provides a way to profile code.

Installation

$ composer require symfony/stopwatch

Note

If you install this component outside of a Symfony application, you must require the vendor/autoload.php file in your code to enable the class autoloading mechanism provided by Composer. Read this article for more details.

Usage

The Stopwatch component provides a consistent way to measure execution time of certain parts of code so that you don’t constantly have to parse microtime by yourself. Instead, use the Stopwatch class:

use Symfony\Component\Stopwatch\Stopwatch;

$stopwatch = new Stopwatch();

// starts event named 'eventName'
$stopwatch->start('eventName');

// ... run your code here

$event = $stopwatch->stop('eventName');
// you can convert $event into a string for a quick summary
// e.g. (string) $event = '4.50 MiB - 26 ms'

The StopwatchEvent object can be retrieved from the start(), stop(), lap() and getEvent() methods. The latter should be used when you need to retrieve the duration of an event while it is still running.

Tip

By default, the stopwatch truncates any sub-millisecond time measure to 0, so you can’t measure microseconds or nanoseconds. If you need more precision, pass true to the Stopwatch class constructor to enable full precision:

$stopwatch = new Stopwatch(true);

The stopwatch can be reset to its original state at any given time with the reset() method, which deletes all the data measured so far.

You can also provide a category name to an event:

$stopwatch->start('eventName', 'categoryName');

You can consider categories as a way of tagging events. For example, the Symfony Profiler tool uses categories to nicely color-code different events.

Tip

Read this article to learn more about integrating the Stopwatch component into the Symfony profiler.

Periods

As you know from the real world, all stopwatches come with two buttons: one to start and stop the stopwatch, and another to measure the lap time. This is exactly what the lap() method does:

$stopwatch = new Stopwatch();
// starts event named 'foo'
$stopwatch->start('foo');
// ... some code goes here
$stopwatch->lap('foo');
// ... some code goes here
$stopwatch->lap('foo');
// ... some other code goes here
$event = $stopwatch->stop('foo');

Lap information is stored as “periods” within the event. To get lap information call:

$event->getPeriods();

In addition to periods, you can get other useful information from the event object. For example:

$event->getCategory();   // returns the category the event was started in
$event->getOrigin();     // returns the event start time in milliseconds
$event->ensureStopped(); // stops all periods not already stopped
$event->getStartTime();  // returns the start time of the very first period
$event->getEndTime();    // returns the end time of the very last period
$event->getDuration();   // returns the event duration, including all periods
$event->getMemory();     // returns the max memory usage of all periods

Sections

Sections are a way to logically split the timeline into groups. You can see how Symfony uses sections to nicely visualize the framework lifecycle in the Symfony Profiler tool. Here is a basic usage example using sections:

$stopwatch = new Stopwatch();

$stopwatch->openSection();
$stopwatch->start('parsing_config_file', 'filesystem_operations');
$stopwatch->stopSection('routing');

$events = $stopwatch->getSectionEvents('routing');

You can reopen a closed section by calling the openSection() method and specifying the id of the section to be reopened:

$stopwatch->openSection('routing');
$stopwatch->start('building_config_tree');
$stopwatch->stopSection('routing');