Let’s say you want to measure how long myFunction takes:

function myFunction(): void
{
    sleep(1); // 1 second
}

To write a quick benchmark, you can use microtime and number_format:

$time = microtime(true);
myFunction();
$elapsed = microtime(true) - $time;
echo number_format($elapsed, 3); // 1.000

Basic Function

To create a basic function from the code above:

function benchmark(): float
{
    static $time;
    if (is_null($time)) {
        $time = microtime(true);
        return 0;
    }
    return microtime(true) - $time;
}

This allows you to refactor the example to the following:

echo number_format(benchmark(), 3); // 0.000
myFunction();
echo number_format(benchmark(), 3); // 1.000

Advanced Function

For a more advanced function that allows multiple entries to be stored and reset:

/**
 * Benchmarks elapsed time for a given entry.
 *
 * @param string $key
 * @param bool $reset
 * @return float
 */
function benchmark(string $key = '', bool $reset = false): float
{
    static $entries = [];
    if ($reset) {
        unset($entries[$key]);
    }
    if (empty($entries[$key])) {
        $currentTime = microtime(true);
        $entries[$key] = $currentTime;
        return 0;
    }
    $currentTime = microtime(true);
    $previousTime = $entries[$key];
    $elapsedTime = $currentTime - $previousTime;
    return $elapsedTime;
}

The function can be used like so:

echo number_format(benchmark('myFunction'), 3); // 0.000
myFunction();
echo number_format(benchmark('myFunction'), 3); // 1.000
echo number_format(benchmark('myFunction', true), 3); // 0.000

Demo

Check out the Repl.it of the advanced function: