Calculate time difference button - php

Question

Hi I am new to javascript and php. I have a form that has three text boxes, starttime, endtime and results. I am trying to take the starttime and endtime and find how much time has passed and display this in the results. How can I go about this?
here is my html:
<form action="JobChangeTimeSheet.php" method="GET">
Machine Stopped at:
<input type="time" name="start_date"/>
End of TO:
<input type="time" name="since_start"/>
<input type="submit">
Total time
<?PHP
if (! empty($_GET['start_date'])){
$start_date = new DateTime($_GET['start_date']);
$since_start = $start_date->diff(new DateTime($_GET['since_start']));
echo $since_start->days.' days ';
echo $since_start->h.' hours';
echo $since_start->i.' minutes';
}
?>
</form>
You can see there are 2 text boxes, a button, and a third disabled text box. I am trying to view the difference in minutes between the two text boxes in the third text box

Answer 1

Since you do not have a code I can work on, I will guide you exactly through the steps on how to do this.
Load your HTML input in PHP vars named $start_date and $end_date. Use these lines:
$start_date = new date("Y-m-d H:i:s",strtotime($start_date));
$end_date = new date("Y-m-d H:i:s",strtotime($end_date));
$interval = $start_date->diff($end_date);
$hours = $interval->format('%h');
$minutes = $interval->format('%i');
echo 'Difference in minutes is: '.($hours * 60 + $minutes);
PS: You are talking about Javascript in your question but no Javascript code has been presented in your code. Are you using some sort of DateTimePicker?