<?php
function syndicate_flight_time($cxn) {

$Syndicate = $_SESSION['Syndicate'];
$sql = "SELECT Landing, Take_Off FROM flight_log WHERE Syndicate_Name = '$Syndicate'";
$result = mysqli_query($cxn,$sql)
    or die ("Can't collect Group Take Off and Landing times");
    while($row = mysqli_fetch_assoc($result)) {
        $difference = (strtotime($row['Landing']) - strtotime($row['Take_Off']));
        $total_diff += $difference;
        $hours = floor($difference/60/60); // rounds the hours to the nearest hour.
        $minutes = (($difference - ($hours * 60 * 60))/60); // rounds the remainder of the hours to the nearest minutes.
        $time = $hours.":".$minutes; // puts a : between the hours and minutes.
        echo '<br />'.$time;
    }
}

$total_hours = floor($total_diff/60/60); // rounds the hours to the nearest hour.
        $minutes = (($total_diff - ($total_hours * 60 * 60))/60); // rounds the remainder of the hours to the nearest minutes.
        $total_time = $hours.":".$minutes; // puts a : between the hours and minutes.

echo "total time:".$total_time;

?>