I'm having trouble calculating the number of hours worked. 
We start with a time which starts as a string in this case ($time).
Then we change the time to 00:00:00 and store the result as a new variable ($newtime).
Then we need to calculate the difference between $time and $newtime but there is a formatting issue which I do not fully understand. Would anyone help?

```
$time = "2017-09-01 11:00:00"; //must start as a string like this
$newtime = new DateTime($time);
$newtime->setTime(00, 00,00); //change time to 00:00:00
$worktime = round((strtotime($time) - $newtime)/3600, 2);
echo "Hours Worked: " . $worktime . "<br>";

```