PHP gets target function execution time

/**
 * class EfficiencyTester
 * Efficiency tester, test the running time of functions
 * @version 1.0 2013.04.13
 * @author Kross
*/
class EfficiencyTester {
    /**
 * var $testTimes
 * Number of tests
*/
    private $testTimes = 1000;
    /**
 * function getTime()
 * Get the timestamp according to the time mode
 * @param $timeModel time mode, default: microseconds
 * @return int timestamp
*/
    private function getTime($timeModel = 'MS') {
        if ($timeModel == 'MS') {
            return microtime();
        } else if ($timeModel == 'S') {
            return time();
        } else {
            return microtime();
        }
    }
    /**
 * function testOnce()
 * Test the target function once and return the running time
 * @param $functionName Target function name
 * @param $timeModel Time mode, default: microseconds
 * @return double The time for the target function to run once ( Very random)
*/
    public function testOnce($functionName, $timeModel = 'MS') {
        $startMicroTime = $this->getTime($timeModel);
        $functionName();
        $endMicroTime = $this->getTime($timeModel);
        $costMicroTime = $endMicroTime - $startMicroTime;
        return $costMicroTime;
    }
    /**
 * function test()
 * Test the target function multiple times and return the running time (average)
 * @param $functionName Target function name
 * @param $timeModel Time mode, default: microseconds
 * @return double Target function Running time
*/
    public function test($functionName, $timeModel = 'MS') {
        $totalMicroTimes = 0;
        for ($i = 1; $i <= $this->testTimes; $i++) {
            $totalMicroTimes += $this->testOnce($functionName);
        }
        return $totalMicroTimes / $this->testTimes;
    }
}
?>

测试代码：

require_once('../class/EfficiencyTester.class.php');
$e = new EfficiencyTester();
echo $e->test('rand');
?>

一开始直接使用 microtime() 获取时间的，后来考虑到如果想获得单位是秒的运行时间，这样写就不够多态了，然后就写了一个getTime() 的函数来获取不同单位的时间戳。 如此貌似目标函数的运行时间变长了，可能是因为 getTime() 函数中的判断占用了一部分时间。