add column values from a selected range in code igniter

time-recods table i have

date
time in 
time out 
break in
break out
total_time 

fields in my table. i have this sql query

public function showattendance(){

    $start      = $this->input->post('DATE_FROM');
    $end        = $this->input->post('DATE_TO');
    $employee   = $this->input->post('ID_NUM');

    $sql = "SELECT * FROM `attendance` WHERE (DATE BETWEEN '".$start."' AND '".$end."') AND (ID_NUM = '".$employee."')";

    $query = $this->db->query($sql);

    return $query->result();
}

now all i want to do is when i already selected the rows between the dates i chose, i wanted to add the selected data from total_time column.

for example i got an array of

array = (
ID[0] => '1' , TOTAL_TIME[0]=>'09:30'
ID[1] => '2' , TOTAL_TIME[1]=>'07:30'
ID[2] => '3' , TOTAL_TIME[2]=>'08:30'
ID[3] => '4' , TOTAL_TIME[3]=>'09:00'
ID[4] => '5' , TOTAL_TIME[4]=>'05:45'

);

all i want to do is to add

TOTAL_TIME[0]+TOTAL_TIME[1]+TOTAL_TIME[2]+TOTAL_TIME[3]+TOTAL_TIME[4] = $value

It gets pretty simple to do so when you convert your result into array.. This might help you out from your problem.

Here one column is later updated with new values in php. This may be helpful.

-------------- Updated Answer ------------

Then your array should be like

<?php
$x =  array(
    array( ID => '1' , TOTAL_TIME =>'09:30'),
    array( ID => '2' , TOTAL_TIME =>'07:30'),
    array( ID => '3' , TOTAL_TIME =>'08:30'),
    array( ID => '4' , TOTAL_TIME =>'09:00'),
    array( ID => '5' , TOTAL_TIME =>'05:45'));

$total;
foreach($x as $y){
    $total+=$y["TOTAL_TIME"];
}
echo "Total Time = ".$total;

?>

Thus you can get your total time.