The Stopwatch Component

The Stopwatch Component

The Stopwatch component provides a way to profile code.

Installation

You can install the component in two different ways:

Then, require the vendor/autoload.php file to enable the autoloading mechanism provided by Composer. Otherwise, your application won't be able to find the classes of this Symfony component.

Usage

The Stopwatch component provides an easy and 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 simple Stopwatch class:

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use Symfony\Component\Stopwatch\Stopwatch;

$stopwatch = new Stopwatch();
// Start event named 'eventName'
$stopwatch->start('eventName');
// ... some code goes here
$event = $stopwatch->stop('eventName');

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.

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.

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:

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$stopwatch = new Stopwatch();
// Start 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:

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$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:

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$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');

This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.