我的方法是使用hrtime，它是为性能指标而创建的，它独立于系统时间。Hrtime不受系统时间变化的影响。hrtime自PHP 7.3.0起可用

$start = hrtime(true);
sleep(5); // do something, in your case a loop
$end = hrtime(true);
$eta = $end - $start;
// convert nanoseconds to milliseconds
$eta /= 1e+6;
echo "Code block was running for $eta milliseconds";

输出:

代码块运行了5000.495206毫秒

下面是一个返回小数秒的实现(即1.321秒)

/**
 * MICROSECOND STOPWATCH FOR PHP
 *
 * Class FnxStopwatch
 */
class FnxStopwatch
{
    /** @var float */
    private $start,
            $stop;

    public function start()
    {
        $this->start = self::microtime_float();
    }
    public function stop()
    {
        $this->stop = self::microtime_float();
    }
    public function getIntervalSeconds() : float
    {
        // NOT STARTED
        if (empty($this->start))
            return 0;
        // NOT STOPPED
        if (empty($this->stop))
            return ($this->stop - self::microtime_float());

        return $interval = $this->stop - $this->start;
    }

    /**
     * FOR MORE INFO SEE http://us.php.net/microtime
     *
     * @return float
     */
    private static function microtime_float() : float
    {
        list($usec, $sec) = explode(" ", microtime());

        return ((float)$usec + (float)$sec);
    }
}

下面是我用来测量平均时间的脚本

<?php

$times = [];
$nbrOfLoops = 4;
for ($i = 0; $i < $nbrOfLoops; ++$i) {
    $start = microtime(true);
    sleep(1);
    $times[] = microtime(true) - $start;
}

echo 'Average: ' . (array_sum($times) / count($times)) . 'seconds';

你可以使用微时间功能。从文档中可以看到:

microtime -以微秒为单位返回当前Unix时间戳 如果get_as_float被设置为TRUE，则microtime()返回一个浮点数，它表示当前时间(以秒为单位)，从Unix纪元开始精确到最近的微秒。

使用示例:

$start = microtime(true);
while (...) {

}
$time_elapsed_secs = microtime(true) - $start;

这样会更清楚

<?php

$start = hrtime(true);

while (...) {
}

$duration = hrtime(true) - $start;
echo  $duration * 1000 ." -> microseconds". PHP_EOL; 
echo  $duration * 1000000 ." -> milliseconds". PHP_EOL; 
echo  $duration * 1e6 ." -> milliseconds". PHP_EOL; 

结果

37180000 -> microseconds
37180000000 -> milliseconds
37180000000 -> milliseconds

看()。