PHP Why does the DateTime diff function always return zero?

Question

I have the following code that tries to calculate hours worked. I'm having a bit of an issue in that hours and minutes always returns zero. My best guess is it has something to do with the new DateTime, but I have no idea how to remedy this.

<?php
include_once 'db_connect.php';
include_once 'psl-config.php';
include_once 'functions.php';

$error_msg = "";

sec_session_start();

//Get Username from session id
$username =  htmlentities($_SESSION['username']);

//get time date stamp
date_default_timezone_set('America/Chicago'); //set default timezone, just to be sure


//GET Last Clockin from timesheet table
$result = $mysqli->query("SELECT lastclockin FROM timesheet WHERE username = '$username'");
$number_of_rows =  $result->num_rows;

while ($row = mysqli_fetch_assoc($result)) {
        $lastclockin = $row["lastclockin"];
    }
    echo $lastclockin;
    echo "<br />";

    $now = new DateTime();

    $diff = $now->diff(new DateTime($lastclockin));

$hours = $diff->h;
$minutes = $diff->m;
$hours = $hours + ($diff->days*24);

echo $now->format('Y-m-d H:i:s');
echo "<br />";

echo $hours;
echo "<br />";
echo $minutes;
echo "<br />";
?>

The results are as follows:

2014-09-11 13:02:15
2014-09-11 13:47:34
0
0

Answer 1

There is zero hours difference between the two times so that makes sense. You'll need to test using two times that are further apart to see a value greater than zero here.

Your minutes are incorrect because m is the month identifier. i is for minutes.

$minutes = $diff->i;