ElapasedTiming - MicroTiming

<?php
namespace app\system;

class MicroTime {

    private $when = null;

    private $float = null;
    private $seconds = null;
    private $milliseconds = null;

    // Constructor for class
    public function __construct($when = null) {
        if (is_null($when)) {
            $when = microtime();
        }

        $this->when = $when;
        $this->setSecMSec($when);
    }

    public function elapsedTime()
    {
        return round((float) $this->seconds + $this->milliseconds / 1000.0, 3);
    }

    public function seconds()
    {
        return $this->seconds;
    }

    public function milliseconds()
    {
        return $this->milliseconds;
    }


    public function asfloat()
    {
        return $this->float;
    }

    public function when()
    {
        return $this->when;
    }

    public function asDateTime() {
        return \DateTime::createFromFormat('U,u', $this->seconds .','. $this->milliseconds * 1000);
    }

    // Format time to date and time
    public function asDateTimeStr() {
        $when = date_create_from_format('U', $this->seconds);
        return sprintf("%s.%03u", $when->format('Y-m-d H:i:s'), $this->milliseconds);                  ;
    }

    // always subtract the later from the earlier and change signs if required
    public function diff(MicroTime $then)
    {
        // which is earlier?
        $swapped = false;
        $mtL = $this;
        $mtE = $then;

        if ($mtL->float < $mtE->float) {
            $swapped = true;
            $mtE = $this;
            $mtL = $then;
        }
        $diff = new self();
        $diff->when = $mtL->when;
        $diff->float = $mtL->float - $mtE->float;
        $diff->seconds = (int) floor($diff->float);
        $diff->milliseconds =  (int) round(($diff->float - $diff->seconds) * 1000.0, 0);

        if ($swapped) {
            $diff->float = $diff->float * -1.0;
            $diff->seconds = $diff->seconds * -1.0;
            $diff->milliseconds = $diff->milliseconds * -1.0;
        }
        return $diff;
    }

    /**
     *
     * @param type $when
     * @return array [seconds, milliseconds]
     */
    private function setSecMSec($when)
    {
        if (is_float($when)) {
            $this->float = $when;
            $this->seconds = (int) floor($when);
            $this->milliseconds =  (int) round(($when - $this->seconds) * 1000.0, 0);
        }
        else {
            list($usec, $sec) = explode(' ', $when);
            $this->seconds = (int) $sec;
            $this->milliseconds =  (int) round($usec * 1000.0, 0);
            $this->float = (float) $sec + (float) $usec;
        }
    }

    public function __get($name)
    {
        return $this->{$name};
    }
}